Quantitative evaluation of China's energy supply policies in the ‘13th Five‐Year Plan’ period (2016–2020): A PMC index modelling approach incorporating text mining

Energy supply policy quality is an important factor that would impact national energy security. While existing research conducted policy evaluation from the lens of performance assessment, less study has been devoted to evaluating energy supply policy from the perspective of policy making. This study takes the energy supply policy documents issued by China's central government during the ‘13th Five‐Year Plan’ period (2016–2020) as the research sample, and pioneers the use of the extended policy modelling consistency (PMC) index model combined with the text mining methodology to construct a policy evaluation index system with the characteristics of the energy supply policy which conducts a more in‐depth quantitative evaluation of the energy supply policy documents. The results show that the average PMC index value of China's energy supply policies is 7.26, and the overall quality is high. The concerns of existing policies are mainly focused on reform and development planning, safety production management and project engineering construction, but there is still room for improvement in policy predictability, coordination of policy areas, clarity of policy basis and goals and comprehensiveness of policy tool combinations. Based on this, China should improve the comprehensiveness of its energy supply policy tool combinations in terms of policy design norm; strengthen policy predictability and coordination of policy areas in terms of policy implementation guarantee; and clarify the basis and goals of policies in terms of policy orientation enhancement, to provide a reference basis for the formulation and improvement of future energy supply policies and to realise the sustainable development of energy supply.


| INTRODUCTION
Energy is the foundation of the national economy.In particular, it plays a vital role in guaranteeing the sustained, rapid and healthy development of the economy and in promoting the improvement of people's lives.At present, China has become the world's largest energy producer and consumer and has formed an energy supply system with the comprehensive development of various energy sources. 1 'The Five-Year Plan' is an important policy instrument adopted by the Chinese central government to guide the national economy and social development over a 5-year period.The '13th Five-Year Plan' period is the decisive stage for China to build a moderately prosperous society in all aspects, and it is a crucial period for deepening reform and opening up and accelerating the transformation of the economic development mode. 2 Moreover, the Chinese central government has also drawn up a 13th Five-Year Plan for Energy Development.This plan emphasised the need to focus more on adjusting energy structure and accelerating green and low-carbon development. 3Since the release of this plan, China has implemented a series of policy measures aimed at bolstering energy security, ensuring production and supply for all types of energy enterprises and promoting transformative energy development and low-carbon initiatives.According to the data released by the National Bureau of Statistics of China, the country's total amount of primary energy production reached 4.07 billion tons of standard coal in 2020, indicating a 2.5% increase; raw coal production reached 3.84 billion tons with a year-on-year growth of 0.9%; crude oil production amounted to 190 million tons, showing a 1.6% increase; natural gas production reached 188.85 billion cubic metres, representing a 9.8% increase and electricity generation amounted to 7.4 trillion kilowatt hours, indicating a 2.7% increase.Moreover, after preliminary calculations, China's total amount of energy consumption reached 4.98 billion tons of standard coal in 2020, showing a 2.2% increase.The proportion of coal consumption in total energy consumption decreased by 1%, whereas the proportion of clean energy consumption increased by 1.1%. 4,5It is evident that China's energy supply capacity is being strengthened, and the energy consumption structure has been further optimised.
However, the rapidly increasing trend of energy demand is difficult to change within a short time due to the large economic size and sustained economic growth.Moreover, adjusting the energy structure still faces many practical difficulties that cannot be overcome easily. 6The fact is that China is still facing the challenge of the energy supply revolution, energy supply policies are also made in the way of exploration and the problem of poor policy implementation begins to emerge.The Chinese central government proposes to promote four types of energy revolutions involving energy consumption, energy supply, energy technology and energy systems. 7The new development environments, including the new pattern of energy supply and demand, the new trend of international energy development and the new situation of domestic energy transformation, not only bring challenges but also provide opportunities for the development of China's energy industry.Therefore, it is crucial to scientifically evaluate the country's energy supply policies issued in the '13th Five-Year Plan' (2016-2020) period to provide convincing evidence for the optimisation and improvement of the subsequent policy, facilitating the promotion of an energy supply revolution in the new development stage.
In summary, this study focuses on how to effectively evaluate and analyse the energy supply policies issued by the Chinese central government during 'the 13th Five-Year Plan' period on a multidimensional basis.The value of this study lies in describing and analysing the focus of existing policies and their strengths and weaknesses.Building upon this foundation, this study aims to provide recommendations for formulating and improving China's energy supply policies.In addition, the results of the study can also provide lessons for other countries to optimise their energy supply policies from a policymaking perspective.The novelty of this study lies in the introduction of the policy modelling consistency (PMC) index model and the integration of text mining methods to extend it for the construction of a policy evaluation index system with energy supply policy characteristics so that the policy evaluation results can be more reliable and the results can be analysed more deeply.The model is then used to quantitatively analyse China's energy supply policy for the first time.
The contribution of this study is twofold: first, this study helps in enriching the body of knowledge of the evaluation of energy supply policies; second, by expanding the number of policy samples, taking policy clusters as the research object and constructing an extended PMC index model, this study provides an objective and comprehensive quantitative evaluation of these energy supply policies to provide a reference basis for the formulation, optimisation and improvement of future energy supply policies.
The rest of this paper is organised as follows.Section 2 comprises the literature review; Section 3 presents the research methodology, which includes the research design and the specific process of constructing the extended PMC index model; Section 4 discusses the results; Section 5 exhibits the main conclusions and policy suggestions.

| Policy evaluation on energy supply
The existing literature extensively explores energy policy evaluation concerning energy security, energy conservation and renewable energy.In terms of energy security policies, scholars have focused on the combined effect of energy security and other environmental policies.Bollen et al. 8 conducted a comprehensive assessment of climate change, air pollution and energy security policies using an extended MERGE model.Strambo et al. 9 used a simple assessment framework to analyse the coherence degree of EU climate change mitigation and energy security policies.There are varied evaluations of energy conservation policies based on different application areas.For instance, Li et al. 10 summarised the major energy conservation and emission reduction policies in the Chinese power sector and evaluated the results of these policies by analysing several key indicators of energy consumption and emissions.Liu and Qiang 11 constructed a two-dimensional analysis framework of building energy efficiency policies from the perspective of policy tools, used content analysis to code and count the published building energy efficiency policies, conducted analysis and evaluation based on the results.In addition, Lin and Zhu 12 used panel data from 114 cities in China to analyse the impact of energy conservation and emission reduction policies on sustainable urban development.Concerning renewable energy policies, many scholars have tried to evaluate their effects using different methods.For instance, Zhang et al. 13 conducted a systematic analysis of policy disadvantages based on a comprehensive review of China's renewable energy development policies and provided further policy optimisation suggestions.Liv et al. 14 analysed the mechanisms of seven renewable energy generation policies from multiple perspectives using a partial equilibrium model and empirically analysed the effectiveness of renewable energy generation policies in China.Kilinc-Ata 15 applied an econometric framework to assess the effectiveness of renewable energy policies in promoting renewable energy deployment capability in the EU and the United States.
Although studies on policy evaluation on energy policy are ubiquitous, few studies focus on energy supply policies and many of them either focus on the feasibility of the energy supply system or only focus on some specific energy supply policies.For instance, Sengul et al. 16 developed a multi-criteria decision support framework for ranking renewable energy supply systems in Turkey, thus providing decision support to the Turkish government based on the results of the study.Bagdanavicius et al. 17 conducted an energy, exergy and exergoeconomic analysis of four community energy supply systems.In terms of policy evaluation on specific energy supply, Garcia-Alvarez et al. 18 conducted an empirical evaluation of the feed-in tariff and quota obligation policies for promoting solar PV energy between 2000 and 2014 and their policy design elements to verify their effectiveness.Similarly, Wei et al. 19 studied the evolution of China's offshore wind power pricing policy and its impact on the trilemma comprising capacity, pricing and subsidies and provided policy suggestions to promote the development of the country's offshore wind power industry.
In conclusion, policy evaluation research on energy supply policy is limited, with the scope of research needing to be further supplemented.Therefore, the current study considers the energy supply policies issued by the Chinese central government during the 13th Five-Year Plan period as the object of research and evaluates these policies using the PMC index model combined with the text mining methodology to provide a novel analytical idea for the follow-up research on the evaluation of energy supply policy.

| Evolution of policy evaluation methods
Policy evaluation is a complex system project that aims to measure and evaluate policy programmes to provide a basis for policy formulation, adjustment and optimisation. 20Policy evaluation was first introduced in education and public health programmes before World War I. 21 After the 1970s, policy evaluation gradually became an independent field of study from social science evaluation.Suchman 22 initially created a five-category evaluation methodology, followed by Poland's creation of the 'three-E' evaluation categorisation framework 23 and then Wollmann's proposal of classical policy evaluation. 24At present, policy evaluation research is constantly developing, covering areas such as electric vehicle policy, 25 smart grid policy, 26 cultivated land protection policy 27 and science and technology innovation policy. 28hus far, policy evaluation studies have generally been conducted using two major enquiry approaches.One is policy effect evaluation, which evaluates the implementation effect of the policy through the measurement of some indicators but does not evaluate the content of the policy. 29The evaluation methods used include the questionnaire survey method, 30 the fuzzy comprehensive evaluation method 31 and so on, but these methods have limitations; for instance, the questionnaire survey method is costly and lacks sufficient reliability. 32The other is policy content evaluation, which involves conducting a policy evaluation only by evaluating policy content that explicitly presents as policy context per se to determine policy quality. 33The evaluation of the policy content itself is an important basis for obtaining an insight into the inherent strengths and weaknesses of the policy and a prerequisite for improving the implementation effect of the policy.Therefore, this study advocates a quantitative evaluation of the scientificity and reasonableness of the policy content itself to pave the way for the subsequent evaluation of the implementation effect of the policy, which may be in existence.However, existing quantitative evaluation methods for policy texts only consider partial dimensions, and the research conclusions are generally horizontal comparisons and descriptive statistical analysis between policies, 34,35 lacking comparisons of the strengths and weaknesses of the policies themselves.Compared with these existing methods, the PMC index model has its advantages.The PMC index model is a method proposed by Estrada 36 to quantitatively evaluate a single policy based on the content of policy texts.This model is built on the Omnia Mobilis hypothesis, which aims to emphasise that everything in the world is constantly moved, developed and connected.Therefore, it should be considered as comprehensively as possible when setting up variables, without neglecting any possible relevant variables. 37The PMC index model could be used to evaluate the consistency of policies, reflect the strengths and weaknesses of policies intuitively and provide more scientific evidence for policy formulation and improvement.Based on these strengths, the model is clearly applicable to the energy supply policy evaluation conducted in this study.The model has also been widely used in policy evaluation, such as ecological compensation, 38,39 green development, 40,41 fire safety education 42 and fishery insurance. 43n research on energy policy evaluation methods, most scholars apply qualitative methods; for instance, Lo 44 conducted a critical review of renewable energy and energy efficiency policies in the five areas of electricity, industry, transportation, buildings and local government in China and studied the progress and the limitations of China's formulation and implementation of these policies.Similarly, Zhang et al. 45 categorised China's forestry biomass industry support policies and made an in-depth analysis of the problems and then put forward countermeasures and suggestions to improve the country's forestry biomass industry policy system.Moreover, Zheng and Zhang 46 compared the offshore wind power technology promotion policies of China, the United States, the United Kingdom and Germany from the dimensions of policy tools and industrial chain and put forward policy suggestions on the current problems in China.Zeng et al. 47 analysed the evolution and implementation effects of China's renewable energy tariff policy, discussed the problems in the tariff policy and put forward feasible suggestions to solve these problems.Moreover, a few scholars use quantitative methods to assess energy policies; for instance, Zhao et al. 48used a variable intercept and mixed regression model with provincial panel data from 2001 to 2013 to analyse the impacts of price and non-price policies that promote the development of wind power on the growth of installed capacity in different wind resource regions.Existing research on energy policy evaluation methods is mainly qualitative, focusing on theoretical analysis, with less research on the quantitative evaluation of energy policy textual information, thereby making it difficult to objectively and effectively determine the potential characteristics and strengths and weaknesses of related policies.In response to this problem, the current study attempts to quantitatively evaluate China's energy supply policies using the previously mentioned PMC index model to analyse the potential paths for improving energy supply policies from multiple dimensions, with a view to providing more accurate suggestions for future policy formulation and optimisation.However, it is worth noting that the policy index system constructed by the current PMC model is set to be relatively fixed, 49 which makes it difficult to perform an objective and comprehensive evaluation of the policy text content.Therefore, the present research conducts deep text mining on the energy supply policy sample set through the ROSTCM6 (5.8.0.603) tool.According to the results of the semantic network of mined high-frequency words, the PMC index model is extended and optimised, and the energy supply policy evaluation system is originally proposed to achieve a more targeted and objective quantitative evaluation of the policy text.In addition, the existing policy evaluation research results based on the PMC index model mainly model a single policy, the correlation relationship between policies is cutoff, and the comparative analysis among policies and research on policy characteristic distribution dynamics are lacking.In this article, we expand the sample number of policies, cluster the policy texts as a policy group as the research object and then build an extended PMC policy evaluation model to quantitatively analyse it, so that it can evaluate a single policy, compare the strengths and weaknesses of different policies and analyse the characteristics of the policies from different dimensions.

| Research design
The PMC index model, as a method of quantitative policy evaluation, usually measures the consistency of the policy modelling process with a multi-indicator construction, whose construction involves nearly 10 first-level indicators and several second-level indicators, and studies the cumulative effect of each indicator on the overall change.It evaluates the consistency of policy formulation through the construction of indicators and uses the results depicted in a three-dimensional visualisation space to intuitively show the strengths and weaknesses of the policy, which is the biggest difference that distinguishes the PMC index model from other policy evaluations.In general, the construction of the PMC index model includes the following steps: (1) variable selection and parameter setting, (2) multiinput-output table construction, (3) PMC index calculation and (4) PMC surface drawing.In general, the overall use of the PMC index model has undergone initial standardisation.However, the selection of indicators in the PMC index model is relatively fixed, making it difficult to objectively and accurately evaluate the policy.Thus, the current study extends the PMC index model by integrating it with the text mining method.The text mining method is used to conduct social network and semantic network analysis on the policy text, and the results obtained are used as indicators to optimise the original relatively fixed indicators to obtain the indicator system with policy characteristics, which makes the results of policy evaluation more reliable.Simultaneously, the results of text mining policies can further analyse the focus of policy attention and achieve a grasp of the distribution of existing policy attention.
Using the extended PMC index model described above, we divide its construction process into the following steps.First, selection of policy document clusters.The model is not a simple quantification of a single policy but a systematic quantitative analysis of many policies.Second, policy text mining and analysis.Utilising text mining technology to mine policy text is the key to constructing a policy evaluation index system with policy characteristics.Third, determining evaluation indicators.The evaluation indicators are quantitative summaries of the selected policy texts, and the model considers all the realisable variables with the relevant policies to achieve a comprehensive reflection of the policy information.Fourth, PMC index measurement.By calculating the PMC index of the selected policies, the results obtained are used as the analytical basis for policy formulation and optimisation.Figure 1 shows the mentioned construction framework.

| Data selection and pre-processing of policy documents
According to the definition of energy supply and its expansion, we used 'energy supply', 'energy development', 'energy utilisation', and so forth, as the search keywords in this study.The time interval is set from 2016 to 2020, corresponding to China's '13th Five-Year Plan'.All the relevant policies on energy supply were collected from the websites such as the Chinese Law Retrieval System (https://www.pkulaw.com/law), the official website of the National Energy Administration of China and the Chinese government website.After manually removing the duplicate, letters, replies, approvals and other irrelevant documents, 205 policy documents were finally selected as research samples.

| Policy text mining and analysis
In this study, we used ROSTCM6 (5.8.0.603), a text mining software, to extract the top high-frequency words in 205 energy supply policies and filter out the nonsense words to obtain the co-occurrence matrix words.On this basis, we extracted the row feature words to generate the co-occurrence matrix and imported this matrix into Gephi, a complex network analysis software, to build the co-occurrence semantic network of high-frequency words in energy supply policies (as shown in Figure 2) to identify the hot themes of energy supply policy texts.A larger node in the graph indicates that it is associated with more other nodes; the thickness of the lines between the nodes represents the closeness of the connection.The thicker the lines, the closer the connection, making it easier for the nodes to be classified into the same colour (theme).
The colour classification of the semantic network graph shows that there are six hot topics in energy supply policy.After filtering and summarising the keywords contained in each colour, we obtain the following six themes: reform and development planning, safety production management, project engineering construction, supply guarantee mechanism, market trading principle and development and utilisation state.The | 601 policy themes obtained above will serve as an important basis for the subsequent selection of indicators.

| Indicator selection
Being guided by the Omnia Mobilis hypothesis proposed by Estrada et al. 37 and drawing upon the classical variables proposed by Estrada 36 for quantitative policy evaluation and other research frameworks of the existing literature while incorporating the connotative features of energy supply policy texts and the results of policy text mining, we established an indicator system comprising 10 first-level indicators: policy nature, policy timeliness, policy area, policy content, issuing agency, policy evaluation, policy tool, policy object, policy potency and policy disclosure, which are denoted by X1-X10, respectively.We also put forward 39 secondlevel indicators according to the connotation of firstlevel indicators (see Table 1).Among them, the six second-level indicators of policy content (X4) are composed of the six policy themes obtained in the previous section.

| Parameter setting of second-level indicators
After selecting and classifying all the indicators, the parameters of each second-level indicator must be set.To ensure that each second-level indicator has the same degree of importance, all parameter values are set to binary 0 and 1.Thus, when the policy conforms to the corresponding meaning of the second-level indicator, the value is 1; if not, the value is 0. According to this value assignment criteria, the value of each second-level indicator of each energy supply policy document was finally determined.Specifically, to avoid subjective judgement and improve the evaluation accuracy, the second-level indicators in policy nature (X1), policy content (X4) and policy tool (X7) were determined by the text mining method.
The operation of policy nature (X1) and policy tool (X7) is as follows: (1) conducting word segmentation based on the energy supply policy document (the segmented texts are inputted into the Word2vec model 56 for training to generate word vectors); (2) calculating the cosine similarity between word vectors; (3) manually filtering the meaningless feature words to extract the top 10 feature words with similarity to the second-level indicator keywords of policy nature (X1) and policy tool (X7) and ( 4) constructing the feature word lists of the second-level indicators of policy nature (X1) and policy tool (X7) (see Table 2).The feature word frequency is counted to determine whether the policy document contains the contents of the second-level indicators.
For policy content (X4), we used Python (3.9.7) to count the occurrences of indicator keywords in each policy document and set a threshold value of 10.If the occurrences of an indicator keyword in a policy document are greater than or equal to 10 times, then the indicator takes the value of 1; otherwise, it is 0.

| PMC index calculation method
Based on the policy evaluation indicator system, we further calculated the PMC index for the energy supply policy using the following procedures.First, according to Formulas (1) and ( 2), each second-level indicator is assigned a specific value.Second, according to Formula (3), the value of the first-level indicator is calculated.Third, the first-level indicators are summed to obtain the final PMC index.  Here, t is the first-level indicator, j is the second-level indicator and T is the sum of the terms.

| PMC index calculation
According to the abovementioned PMC index calculation method, we take one energy supply policy, Opinions on Accelerating the Utilisation of Natural Gas released in 2017, as an example to show how the method is applied in the specific policy evaluation and to elaborate on the calculation process of the PMC index (see Table 3).
We referred to the policy grading standard proposed by Estrada 36 to classify PMC index scores into four levels: perfect (8.5-10), excellent (7-8.5),acceptable (5.5-7) and poor (0-5.5).Table 4 shows the calculation results of the PMC index for some energy supply policies.

| Distribution characteristic analysis of energy supply policy indicators
To further analyse the characteristics presented by the energy supply policies in different dimensions, we plotted the overall PMC surface of the energy supply policies (Figure 4).Considering the symmetry and balance of the matrix, X10 was removed because the value of X10 was the same in all policies.Finally, a thirdorder matrix was created for surface plotting.We also further observe the distribution characteristics of policies on different indicator dimensions through the violin plotting of the nine first-level indicators (Figure 5) and the mean values situation of the second-level indicators (Table 5) and then identify and analyse the policy samples with abnormal indicators.As shown in Figure 4, the overall PMC surface plot of the energy supply policies is located in a three-dimensional coordinate system, where the x-coordinates of the matrix are denoted as 1, 2 and 3 in the figure, and the y-coordinates are denoted as series 1, 2 and 3.In the PMC index surface, the convex portion corresponds to the higher PMC index, and the recessed portion corresponds to the lower PMC index.It can be seen that the selected energy supply policies perform better in terms of policy nature (X1), policy timeliness (X2), policy evaluation (X6), policy tool (X7) and policy object (X8) and underperform in terms of policy area (X3), policy content (X4), issuing agency (X5) and policy potency (X9).
As for policy nature (X1), the mean value of the PMC index for policy nature is 0.84, indicating that the nature of China's energy supply policies is relatively comprehensive.A total of 77% of them have three natures of supervisory management, a mandatory requirement and encouraging guidance, which indicates that China is taking active incentives to mobilise the enthusiasm of energy enterprises, conducting rigorous supervision and safety checks on energy engineering construction and implementing energy supply policies with strict rules.In addition, only 51% of the policies contain all four natures, which offers a reminder that China's energy supply policy must be improved in terms of predictive assessment.
In terms of policy timeliness (X2), 96% of the policies are effective in the long term, and only 4% are effective in the short and medium terms.Combined with a review of specific policy texts, we find that most of the policies that are effective in the short and medium terms have been decided to be repealed due to the need to implement the relevant requirements and thus have a relatively short validity period.For instance, the Notice of the National Development and Reform Commission on Matters Relating to Comprehensively Promoting the Pilot Reform of Electricity Transmission and Distribution Tariffs was decided to be repealed to implement the requirements of the CPC Central Committee and the State Council regarding the in-depth promotion of simplification of government and decentralisation of power, combination of administration and optimisation of services and the improvement of the business environment. 57n terms of policy area (X3), the mean value of the PMC index for the policy area is 0.51, indicating that most policies limit their policy planning to 1-2 areas.It is worth noting that only 11% of the policies considered all areas.We can conclude that energy supply development actually involves multiple areas and is influenced by multiple factors, which means we must identify the inherent connections among varied areas.In addition, as can be seen from Table 5, the percentages of policy texts   As for policy content (X4), the mean value of the PMC index for policy content is only 0.45, indicating that the energy supply policy content is relatively centralised and prominent.It is worth noting that 11 energy supply policies were made with considering all the contents.Most of these policies are related to the '13th Five-Year Plan' for energy development.For instance, the 13th Five-Year Plan for Renewable Energy Development is the policy issued by the National Development and Reform Commission to promote the sustainable and healthy development of the renewable energy industry; therefore, it made considerate plans in promoting renewable energy development and utilisation, base construction, and supervision work. 58n terms of issuing agency (X5), 74% and 45% of the energy supply policies were issued with the participation of the State Council ministries and the national bureaus under their management.Specifically, the National Energy Administration is the main agency for energy management in China, managed by the National Development and Reform Commission; therefore, most energy-related policies are issued by them.Although the number of policies directly issued by the National People's Congress and its Standing Committee and the State Council is only 6, all of them have a macro-planning effect that can send out strong policy signals for energy supply development.
Concerning policy evaluation (X6), the mean value of the PMC index for the policy evaluation is 0.91, which shows that the overall normalisation of the selected energy supply policies is high.A total of 62% of the policies are formulated based on the existing macro policies or instructions of an important meeting with clear goals, scientific and rational planning and specific and detailed content.In addition, the percentages of policies with sufficient basis, clear goals, scientific planning and detailed content are 73%, 89%, 100% and 100%, respectively, indicating that some policy documents do not have sufficient basis and clear goals, leading to deviation in the value of this indicator.
Concerning policy tool (X7), the most commonly used policy tools for energy supply policies are institutional norm (X7: 3.99%); goal planning (X7: 5.98%); infrastructure construction (X7: 2.92%); convenience service (X7: 4.86%) and fiscal, taxation and financial (X7: 1.57%).A total of 46.8% of the energy supply policies use all five of these tools simultaneously, whereas only 2.4% of the policies use only one or two of the five tools, indicating that the development of energy supply must rely on a relatively comprehensive set of policy tools: in the early stage, the government creates a favourable development environment for energy enterprises by enhancing funding allocation and infrastructure construction.During the energy supply period, government agencies would turn their attention to focus on generating institutional constraints on enterprises and clarifying their supply goals to provide a service guarantee for society.In addition, in terms of the performance of the various policy instruments, the policy instrument of fiscal, taxation and finance has performed poorly, indicating that the government must still increase its investment in fiscal, taxation and finance to ensure the comprehensive development of energy supply.
In terms of policy object (X8), the mean value of the PMC index for policy object is 0.94, indicating that most of the energy supply policies are directed at relevant enterprises nationwide.However, there are also a small number of policies that are issued for a certain region or industry.For instance, the Notice on Effectively Doing a Good Job of Urban Heating Work in Northern Heating Areas this Winter and Next Spring is a typical and exceptional policy, which was formulated to ensure a regular launch of the clean heating project in the northern regions and the normal promotion of various tasks of heating in 2017 with detailed working arrangements. 59n terms of policy potency (X9), 96% of energy supply policies have the potency level of departmental rules, indicating that almost all energy supply policies are formulated in accordance with laws and administrative regulations.Although only two policies are laws, they all have very strict provisions and regulate energy supply development with a very high level of legal potency.

| Topic attention analysis of energy supply policies
In addition to analysing the results from the above two dimensions, the present study further analyses the results of the semantic network graph obtained from policy text mining to achieve a grasp of the allocation of topic attention to existing policies, thereby enabling a more comprehensive evaluation of energy supply policies.Figure 2 depicts that reform and development planning, project engineering construction and safety production management are the primary topics addressed in China's energy supply policy during the '13th Five-Year Plan' period concerning about.The market trading principle also got much more attention than other themes, whereas some themes got less attention, such as the supply guarantee mechanism, development and utilisation state.
The '13th Five-Year Plan' period is a key development stage for implementing a new round of energy revolution in China; thus, the Chinese central government paid great attention to the reform and development plan for energy supply during this period.Since the Outline of the 13th Five-Year Plan for National Economic and Social Development of the People's Republic of China proposed a requirement of making a strategic plan for energy reform, China has released the 13th Five-Year Plan for Energy Development as a directive policy document and issued plenty of specific reform plans for different types of energy.Specifically, in the area of renewable energy sources, the government has made clear provisions for the supply capacity and consumption volume of renewable energy sources, such as solar energy, biomass energy and geothermal energy.At the same time, the government has also put forward green development goals including the adjustment of the energy structure, particularly the optimisation of the energy structure by increasing the share of renewable energy in power generation.These efforts do provide feasible operational guidelines for the development of China's energy supply.
Project engineering construction and safety production management are the foundations of energy supply guarantee; thus, they have been highly stressed by the Chinese central government.China has continuously tried to expand project engineering construction and strengthen safety production management.On the one hand, the central government formulated a construction list of annual major energy supply projects according to the construction requirements relating to the planning of energy production and supply and further made special plans according to the energy demands in different regions.On the other hand, the Chinese central government strongly emphasises energy safety production and puts safety production in the first place; therefore, the government has detailed the working measures and classified the responsibilities at all levels to ensure a safe, reliable, adequate and orderly supply of energy.In addition, it can be seen from the energy resources associated with the theme of production safety management in Figure 2 that coal mining resources have become the main focus of energy production safety, which can be inferred that China is still in a transitional period of energy structure reform, as its energy supply is still dominated by traditional energy sources.
The topic attention of the market trading principle was put on the power level.Owing to the unstable situation of the power supply, the Chinese central government has adopted more active measures to overcome the dilemma.Chinese President Xi Jinping has advocated promoting the energy revolution and restoring the commodity attributes of energy.Under this guideline, China has successively implemented a series of reforms to the energy system, which focuses on the decisive role of the market in allocating resources and the fundamental role of the government.Among them, electricity power system reform became a top priority.Specifically, the government has issued relevant policies in which the goal of deepening reform in terms of pricing, trading and operating mechanisms has been proposed.The policies also included the requirements of improving the price trading principles of the electricity market through specific measures, such as building an electric power trading centre and constructing a 'medium and long term + goods in stock + auxiliary service' electricity power market system, to achieve a long-term stable supply of electricity.
The development and utilisation of energy and the improvement of the energy supply guarantee mechanism are less emphasised than other topics, but they are still hot topics in energy supply policies.The monitoring of energy development and utilisation can reflect the degree of demand for energy in different regions.Based on this, the government can adjust the degree of development and utilisation and finally construct a virtuous circle of energy utilisation.Such effort provides an important evaluation indicator for the energy supply guarantee mechanism, which, in turn, guarantees the continuous and stable supply of energy.

| Conclusions
Energy is the material basis for human survival.A good energy supply is related to the stable operation of the national economy and people's livelihood.This study adopts the extended PMC index model to quantitatively evaluate 205 energy supply policies issued by the Chinese central government during the '13th Five-Year Plan' period from three dimensions, including overall policy quality, policy indicator distribution characteristics and policy attention.The results affirm that the overall quality of energy supply policies is high, most of them are of excellent grade, but there remains some room for improvement.At the same time, the distribution characteristics of policy indicators are evident, but there are still some problems, such as insufficient predictability of policy contents, weak coordination in policy areas, vague policy basis and goals and an incomprehensive combination of policy tools.In addition, in terms of policy attention, the focus of energy supply policies is mainly on reform and development planning, project engineering construction and safety production management.From the perspective of policy design, the government and policymakers should focus on dealing with the problems of policy predictability, coordination in policy areas, clarity of policy basis and goals and a comprehensive combination of policy tools.
However, the present study only focuses on the evaluation analysis of the textual content of China's energy supply policies, and it still has some limitations, which can be improved in the following aspects.First, expanding the research sample.The energy supply policies selected in this article are all from the Chinese central government and were issued during the '13th Five-Year Plan' period; thus, the strategic and comprehensive policies account for a high proportion, and the time span of the policies is very small.In the future, we can analyse the policy evolution in different periods by extending the time span.Moreover, we can consider local policies with local characteristics as important supplements to the research sample and compare the characteristics and differences of energy supply policies in different regions.Second, predicting the new frontier to improve policy evaluation.The energy supply policy documents in the present study represent the current status of policies, and we did not combine frontier trends in energy supply to identify the policy problem.In the future, we can continue to perform supplementary analysis by studying frontier trends to identify the key points for future energy supply policy improvement.

| Suggestions
Based on the results of the policy evaluation of China's energy supply, we put forward a series of policy suggestions in terms of policy design norms, policy implementation guarantee and policy orientation enhancement, which would provide implications for China and other countries to formulate or revise energy supply policy.
1. Policy design norm: Improving the comprehensiveness of the combination of energy supply policy tools and establishing and improving the energy supply policy framework system.The 13th Five-Year Plan Outline for National Economic and Social Development of the People's Republic of China released in 2016 clearly stated in the chapter on building a modern energy system that we should deepen the energy revolution; focus on promoting changes in energy production and utilisation methods; optimise energy supply structure; improve energy utilisation efficiency; build a clean, low-carbon, safe and efficient modern energy system and maintain national energy security. 60As an important construction part of China's modern energy system, energy supply reform has been highly valued by national governments and enterprises at all levels during the '13th Five-Year Plan' period.However, due to the special characteristics of energy supply reform, such as large upfront investment, long duration and uncertain effect, a targeted, systematic, perfect and organically synergistic policy system has not yet been established, the combined application of policy tools in the existing policy design is not yet comprehensive, and the supply-oriented policy tools, such as fiscal, taxation and finance, are less applied in the existing policy design, which must be further strengthened and improved.In the future, the necessary incentive mechanism should be constructed, fiscal, taxation and financial inputs should be increased to provide sufficient financial support for the energy supply reform, and the coverage of fiscal, taxation and financial policy tools in policy design should be improved.This is to form a comprehensive energy supply policy framework system with Chinese characteristics, which will provide good policy support for the energy supply reform.2. Policy implementation guarantee: Enhancing policy predictability and building coordinated linkages of multiple policy areas.Because energy supply is impacted by multiple factors, making energy supply plans selectively from economic, technical, social or environmental aspects will not only lead to low efficiency of energy supply but also affect the policy implementation effectiveness.Therefore, it is necessary to establish an effective coordination and linkage mechanism.Specifically, on the one hand, the government should not only focus on stimulating energy supply through financial support and tax incentives but also consider how to technically improve energy supply efficiency through technical innovation.Moreover, the government should consider reducing energy costs to ensure people's livelihood energy supply, advocating clean and efficient utilisation of energy.On the other hand, the government must balance the relationship between different policy areas and find a balance point of energy development that is clean, economic and efficient.This means that the government should pay attention to the economy and the affordability of ordinary people and clean and efficient development of energy.In addition, in terms of the policy nature, because the government pays more attention to the safe production management and construction of energy supply but ignores the early warning measures before energy security supply, the policy weakness presented in the policy evaluation results is poor predictability.Therefore, enhancing policy predictability is a necessary procedure of energy supply policy.Specifically, the first thing is that the government should strengthen communication and information sharing between the energy management agency and emergency management agency to discover the risks that may occur at different stages and promptly detect the deficiencies in the energy supply.Second, the government should construct a risk assessment and early warning index system to assess the probability of occurrence, intensity, degree of damage and the negative impacts of energy supply risks.Finally, the government should establish an energy supply policy emergency plan in which the application contexts, applicable objects, guarantee methods and activation procedures should be included.3. Policy orientation enhancement: Clarifying the basis and goals of energy supply policies to promote the sustainable development of energy supply.Given that energy supply must be responsive to energy demand, market trends and national development plans, and so on, it is difficult to ensure the scientificity and enforceability of energy supply policies if they are formulated without clear basis and goals.Therefore, it is essential to clarify the basis and goals of energy supply policies.On the one hand, the government should establish a reliable basis for energy supply policy based on detailed data and comprehensive research, including information on energy demand, market trends, technological development and environmental impacts.On the other hand, the government should define the goals of the energy supply policy, such as improving energy security, reducing energy consumption, promoting clean energy development and increasing the diversity of the energy supply.These goals should align with the national development plan for energy supply and should be coordinated with other related policies.In addition, when setting goals, it is also necessary to consider their measurability and operability to measure the effectiveness of policies and guide the implementation of relevant measures.Overall, clarifying the basis and goals of energy supply policies is the prerequisite and foundation for formulating scientific and reasonable energy supply policies.Only by formulating energy supply policies that align with the energy supply situation and the country's long-term development plan, based on a full consideration of various factors, can we ensure the sustainability of energy supply and promote sustainable development of the economy and society.

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I G U R E 2 Semantic network of high-frequency words for energy supply policies.CHENG ET AL.

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A B L E 4 PMC index of energy supply policies (excerpt).
Notice of the National Development and Reform Commission and the National Energy Administration on Printing and Distributing the Guiding Opinions on Promoting the Development of Biomass Heating 1.00 1.00 0.50 0.83 0.40 1.00 1.00 1.00 0.50 1.00 8.23 Excellent Notice of the National Development and Reform Commission and the National Energy Administration on Further Promoting the Reform of Incremental Distribution Business 0.75 1.00 0.25 0.50 0.40 1.00 1.00 1.00 0.50 1.00 7.40 Excellent Notice of the National Development and Reform Commission and the National Energy Administration on Further Regulating the Order of Starting Construction of Electric Power Projects 0.75 1.00 0.25 0.33 0.40 1.00 0.80 1.00 0.50 1.00 7.03 Excellent F I G U R E 3 Histogram of PMC index values for 205 energy supply policies.F I G U R E 4 Surface plot of PMC index.F I G U R E 5 Violin diagram of first-level indicator variables.
Energy supply policy evaluation indicator system.
T A B L E 1 level, 56.1% of the policies belong to the excellent level, 35.1% of the policies belong to the acceptable level and 1.5% of the policies belong to the poor level.As can be seen from the histogram in Figure3, the majority of policies with PMC index values above 7 indicate that the overall quality of energy supply policies is at an excellent level, whereas some policies exhibit low quality and require further improvement.
List of X1 and X7 feature words.Example of calculation process of PMC index for energy supply policy.
T A B L E 5 Mean values of second-level indicators in different dimensions.