Does border enforcement deter unauthorized immigration? The case of Mexican migration to the United States of America


  • Wayne A. Cornelius,

    Corresponding author
    1. Department of Political Science and Center for Comparative Immigration Studies, University of California, San Diego, CA, USA
      Professor Wayne A. Cornelius, Center for Comparative Immigration Studies, University of California-San Diego, La Jolla, CA 92093-0548, USA. Email:
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  • Idean Salehyan

    1. Department of Political Science, University of North Texas, Denton, TX, USA
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Professor Wayne A. Cornelius, Center for Comparative Immigration Studies, University of California-San Diego, La Jolla, CA 92093-0548, USA. Email:


This paper asks whether the migration decisions of unauthorized Mexican immigrants to the USA have been influenced by stronger US border enforcement efforts since 1993 that have sharply increased the physical risk and financial cost of illegal immigration. These measures were supposed to have decreased the probability of successful entry, thereby lowering the expected benefits of migration. We carried out a logistic regression analysis of data from a recent survey of 603 returned migrants and potential first-time migrants in rural Mexico. Our findings indicate that tougher border controls have had remarkably little influence on the propensity to migrate illegally to the USA. Political restrictions on immigration are far outweighed by economic and family-related incentives to migrate. An alternative, labor-market approach to immigration control with higher probability of effectiveness is outlined.


Have US border enforcement efforts deterred unauthorized migration from Mexico? Neoclassical economic theory suggests that wage differentials should matter most in migration decisions, yet border enforcement and other immigration controls are designed to restrict access to labor markets. In the current era of economic globalization, states have insisted on strict immigration controls, even while liberalizing the flow of goods, services, and capital. While some regions of the world – most notably the states belonging to the European Union – have relaxed or eliminated restrictions on migration among member-states, the general trend has been to increase barriers to entry. This pattern is most striking along the US–Mexico border, where since the early 1990s there has been a step-level increase in resources and personnel to prevent the entry of undocumented migrants. But the recent deployment of ships, planes, and advanced radar systems by EU members to interdict Europe-bound African migrants at sea suggests a similar commitment to border enforcement as the primary instrument of immigration control.

This paper asks whether “policy matters” in the migration decisions of Mexican immigrants to the USA. Has increased vigilance to stop undocumented migration along the 2,000-mile US–Mexico border had a significant influence on propensity of individuals to migrate? Enhanced border enforcement efforts promised to decrease the probability of successful unauthorized entry, thereby lowering the expected benefits of migration. In addition, the evidence suggests that since the initiation of “Operation Gatekeeper” and other such concentrated border enforcement initiatives, the risk of death and injury as a consequence of clandestine entry has increased sharply, along with the fees that professional people-smugglers charge for their services (Cornelius 2001, 2005; Reyes et al. 2002). Do these increased costs and risks deter potential migrants? Or do persisting economic incentives to migrate outweigh these considerations?

Theoretically, answers to these questions shed light on the role of the state in managing migration and controlling its borders. Determining who is allowed access is a key ingredient of state sovereignty (Guiraudon & Lahav 2000; Rudolph 2003, 2006). If current border enforcement efforts do little to counteract labor-market forces, then the ability of the state to enforce its immigration laws is undermined.1 On a practical level, gaining a better understanding of migration decisions can help in formulating better immigration control policies. With more than 400,000 Mexican migrants entering the USA each year, the choice of immigration policy has a profound influence on economic outcomes in both countries and the fortunes of migrants themselves.

In this paper we seek to determine whether the perception of danger and/or difficulty in illegally crossing the border in the current period of heightened border controls has a significant influence on the propensity to migrate. Previous research has sought to measure the deterrent effect of border enforcement by correlating survey data on decisions to migrate with aggregate measures of changes in the US border enforcement effort (numbers of Border Patrol agents deployed, line-watch hours, apprehensions made) and changes in economic performance on both sides of the border (Espenshade 1995; Espenshade & Acevedo 1995; Hanson & Spilimbergo 2001; Reyes et al. 2002; Cerrutti & Massey 2004; Orrenius 2004; Bean & Lowell 2007). Although our results are generally consistent with those of these researchers, who found that increased enforcement resources deployed along the border have had little effect on the probability of undocumented migration, our approach differs from theirs in that it uses direct evidence on the migrant’s own perceptions of danger and difficulty in crossing the border clandestinely.2 The actual resources deployed may be less important than the effect of border enforcement on the perceptions of potential first-time migrants and repeat migrants in Mexico. Our study collected individual and community-level data that enable us to establish direct linkages between changes in immigration control policy (i.e., the implementation of the post-1993 strategy of concentrated border enforcement) and the propensity to migrate.

Literature review: The political economy of international migration

According to classical economic models of factor mobility, differences in factor endowments between two countries should lead to migration out of labor-abundant countries and into labor-scarce regions until the price of labor converges to an equilibrium wage. Quite simply, workers are expected to move to areas where wages are higher. In the case of the USA and Mexico, the average hourly wage in Mexico in 2000 was approximately $1.80 (Chiquiar & Hanson 2005). With wages even for unskilled undocumented workers averaging 4–6 times this amount in the USA, there are powerful economic incentives for people to migrate north. Another economic perspective focuses on the family rather than the individual as the locus of migration decision-making. The sending of remittances to family members who remain in the country of origin can significantly improve on their consumption and investment habits, providing strong social pressures to send at least some members of the household to work abroad (Taylor 1999). Inter-family comparisons of wealth and status between those who receive remittances and those who do not place additional pressures on working age members of the household to migrate to counter this income inequality.

Although economic and sociological theories of international migration have dominated the published work, political scientists have called for a deeper understanding of the politics of international migration (Hollifield 2000; Cornelius & Rosenblum 2005). Whereas labor-market forces are clearly important in shaping the migration decisions of individuals and households, nation-states determine the terms of access to the domestic labor force. States impose immigration controls to shape the overall supply of labor as well as the quality of the labor force. For instance, although most Western industrialized nations provide relatively few visas for unskilled foreign labor, there is strong competition among them to attract highly skilled migrants with advanced degrees (Cornelius et al. 2001). In addition, there have been bolder measures in most OECD countries to fortify national boundaries against the unauthorized entry of “undesirable” migrants (Andreas & Snyder 2000; Geddes 2000; Cornelius et al. 2004; Lahav 2004).3 Despite the academic discourse about economic integration and the emergence of a “borderless world” (Ohmae 1996; Sassen 1996), enhanced migration controls suggest different standards with respect to particular types of flows. Therefore, an individual’s utility for migrating is not a simple function of wage differentials, but must be discounted by the probability of successful entry into the labor market, and this is determined by the state’s immigration policies.

However, economic theory would also suggest that immigration restrictions – just as capital controls and trade barriers – lead to a suboptimal allocation of economic resources as they reduce the supply of labor below that which the market would decide. This undersupply should in turn lead to the creation of a “black-market” for immigrant labor to meet the unmet demand for workers. Indeed, recent years have brought the emergence of elaborate human smuggling operations that rival the international drug trade in terms of ingenuity and profitability (Kyle & Koslowski 2001). This illicit entry of people circumvents the sovereign prerogative of the state to control its borders and restrict the entry of foreign nationals; it also empowers organized crime networks. Whereas it is unclear whether a tough public stance against illegal immigration is the sincere preference of government officials torn between restrictionist voters and powerful employer lobbies, several scholars have noted a growing gap between the stated objectives of immigration control policies and the outcomes of such policies (Joppke 1998; Freeman 2002; Cornelius et al. 2004). Thus, the actual impact of immigration control policies on the migration choices of individuals is an important empirical and theoretical question. Immigration restrictions should, in principle, reduce an individual’s propensity to migrate, but imperfections in immigration enforcement provide opportunities to evade such measures.

Policing the US–Mexico border

The early to mid-1990s brought increased pressure on elected officials in the USA to reduce undocumented immigration from Mexico. Thus, while the USA and Mexico were busy liberalizing regional trade and investment – particularly through the North American Free Trade Agreement – immigration restrictions were strengthened. In the US Southwest in particular, fears that undocumented migrants undercut wages, consumed social services, and contributed to crime led to public clamor for increased vigilance at the border. A series of border enforcement efforts beginning with “Operation Hold the Line” (1993) in El Paso and “Operation Gatekeeper” (1994) in San Diego significantly increased the visibility of US Border Patrol agents. During this period, Congress and the President worked together to significantly increase enforcement personnel and resources along the US–Mexico border. Approximately 70 miles of the border were fenced to prevent crossings in urban areas where illegal entry was most visible. In addition, there has been a remarkable increase in the sophistication of surveillance and apprehension technology, including remote video surveillance systems, infrared monitors, seismic sensors that can detect footsteps, helicopters, unmanned aerial vehicles (drones), and computerized databases to identify recidivists and people-smugglers among those apprehended. The number of Border Patrol agents rose from 3,965 in September 1993 to 12,349 in September 2006, and spending on border enforcement grew sixfold during this period. Since Fiscal Year 2002, the growth in spending has outpaced increases in apprehensions being made at the border, so each arrest costs more (Fig. 1).

Figure 1.

The US Border Patrol apprehensions (inline image) and expenditure (inline image).
Source: Authors’ calculations from US Immigration and Naturalization Service (1989–2002) and US Department of Homeland Security (2003–2006) data.

The principal rationale for increasing border enforcement was the doctrine of “prevention through deterrence.” It was believed that by significantly increasing apprehension rates and the visibility of the Border Patrol, potential migrants would be dissuaded from attempting a crossing. In testimony before the House of Representatives, Barbara Jordan, Chair of the Congressionally mandated US Commission on Immigration Reform, remarked, “It is far better to deter illegal immigration than to play the cat and mouse game that results from apprehensions followed by return followed by re-entry. To accomplish a true deterrence strategy will require additional personnel as well as a strategic use of technology and equipment” (House of Representatives 29 March 1995, emphasis added). Again, in economic terms, if the probability of successful entry is low enough, then wage differentials between the two countries should matter less in the decision calculus of potential migrants.

In addition to increasing apprehension rates, which was the explicitly stated aim of government officials at the time, enhancing the US Border Patrol’s capabilities had several important unintended consequences. First, whereas urban areas – for example, San Diego, El Centro, Nogales, and El Paso – witnessed the erection of fences, lighting, and an increase in agents, remote areas in the mountains and deserts along the border were left largely unprotected.4 This has led many migrants to attempt riskier crossing strategies over difficult and dangerous terrain; concomitantly, the risk of injury and/or death has increased sharply in recent years (Cornelius 2001). Between January 1995 and September 2006, there were over 4,045 known migrant fatalities because of unauthorized border crossings; dehydration and hypothermia were the most common causes of death. Second, although the use of professional people-smugglers (“coyotes”) to assist in illegal entry was widespread among Mexican migrants by the late 1980s (see Cerrutti & Massey 2004, pp. 29–30; Cornelius & Lewis 2006, pp. 64–66), the proportion of migrants using smugglers rose further in the post-1993 period. Coyotes are hired to lead migrants through difficult crossing areas, provide fraudulent identity documents, and transport migrants to pick-up points where relatives or employers retrieve them. As the demand for their services increased with tighter border enforcement, people-smugglers have tripled or quadrupled their fees (see Cornelius & Lewis 2006, pp. 67–68).

This discussion suggests that migration decisions by Mexicans without legal documents are a function of several factors: relative wages, the probability of successful entry, the risk of physical harm, and coyote fees are all taken into consideration. Yet, with expected earnings in the USA being several times that in Mexico, it remains to be seen if the costs and risks of crossing the border have deterred a substantial number of Mexicans from migrating without papers. In the sections that follow we will attempt to determine if migrants’ subjective assessment of these added costs have had a significant influence on their plans to go north. Theoretically, those at the “cusp” of migrating should be deterred by these additional factors, but whether there has been a systematic deterrent effect at the individual level has not previously been substantiated.

Research design and methods

We report results from a survey of 603 returned migrants and potential first-time migrants who were interviewed in their homes in Mexico by a team of bilingual US and Mexican interviewers during January 2005. The research sites were Tlacuitapa, Jalisco, and Las Animas, Zacatecas, rural communities with high rates of migration to the USA, located in states that traditionally have sent large numbers of migrants to the USA. The research communities were chosen purposively to take advantage of extensive baseline data from previous surveys of migration behavior conducted in these towns (Cornelius 1976, 1991, 1998; Mines 1981; Goldring 1992).

A standardized questionnaire was administered to at least one adult in every dwelling unit that was occupied during the fieldwork period. Because of the small sizes of the populations of the research communities (800–1,500), no sampling was necessary. In each dwelling, the interviewer was instructed first to interview the male head of household. If the male head of household was unavailable throughout the fieldwork period, interviewers were instructed to interview his wife about her husband’s migration experiences. If at that time the wife volunteered that she had migration experience of her own, she was interviewed concerning her own migration experience as well. After interviewing the head of household, the questionnaire was next administered to all sons and daughters of at least 15 years of age. We administered the standardized questionnaire only to people aged 15–65, as we expected to find most of the current and potential migrants in this age range. Of the 603 persons interviewed, 68% were categorized by interviewers as having their principal base in the sending community, whereas 31% were based primarily in the USA and were making short visits to their hometowns at the time of our fieldwork.

The questionnaire contained a total of 143 items (see Cornelius & Lewis 2006, appendix A). In addition to questions pertaining to basic demographic attributes, the questionnaire contained sections on employment and residency in 2004; the migratory history of the family from 1995 to 2005; the migratory history of the interviewee; intentions to migrate in the 12 months following the interview; employment and life in the USA; perceptions of the interviewee’s hometown and his economic situation; and plans for the future. Although most of the questions were closed, open-ended questions were included to elicit more fine-grained information on various aspects of the US migration experience. The average administration time was 50 minutes.


In general, if the “prevention through deterrence” strategy were effective, we would expect people to become less inclined to migrate as: (i) their information about enhanced US border enforcement measures increases; (ii) perceptions of risk and danger increase; (iii) actual negative experiences during past crossings increases. A show of force at the border can only be effective if people are aware of heightened restrictions and that they perceive and/or have actually experienced that such policies make crossing much more difficult. An ideal test of deterrence theory would gauge people’s attitudes before and after the implementation of border enforcement policies. We cannot do so with our cross-sectional research design. However, we are able to determine if our respondents’ knowledge, perceptions, and experience with border enforcement policies are important determinants of their decisions to migrate. Thus, we can estimate the relative significance of economic/demographic factors and immigration control policies.

Our main dependent variable for the analysis that follows (Q71) asks whether the person being interviewed intends to migrate at some time during 2005.5 While we realize that there may be some slippage between stated intentions in January 2005 and actual migration outcomes during the year, we believe that this question can reliably get at the type of person who is most likely to migrate. Of the people who responded to this question, 51% responded in yes, that they have at least considered migrating to the USA.

One way of ascertaining a deterrent effect is to simply ask the “no” respondents why they do not wish to migrate. As such, we asked these people to give the main reason why they were not willing to migrate (Q77). Although lack of economic need, lack of interest, and family considerations dominated the responses to this question, 41 people answered that difficulty crossing was their main reason for staying home, whereas an additional 14 people answered that they could not afford coyote and/or transportation costs. In all then, 55 out of 603 survey respondents indicated that they were deterred from crossing because of the direct or indirect effects of US Border Enforcement policies.6 However, it is also important to consider the perceptions, information, and experiences of those who do wish to migrate along with additional control variables.

As our main variables of interest, we include survey items dealing with perceptions of difficult and danger crossing the border. One question (Q80) asked about perceptions of difficulty in evading the US Border Patrol in the current period. Six percent of our respondents indicated that it is not more difficult to cross; 23% answered that it is now somewhat more difficult; 66% responded that it is much more difficult to cross; and 5% answered that it is now virtually impossible to cross. A second question (Q78) asked interviewees about their level of information regarding current US Border Patrol policies. People were asked if they were aware of current efforts to make unauthorized crossings into the USA more difficult. In answering this question, 72% of the respondents indicated that they were aware of heightened security at the border. Third, we asked a question (Q84) about the perceptions of danger in crossing without legal documents. The overwhelming majority (80%) of survey respondents answered that it is very dangerous to cross; only 20% believed that it is only somewhat dangerous or not at all dangerous. Although this question is subjective, we also asked people if they actually knew someone who had died while attempting to cross into the USA (Q85), as people who knew someone who died may be more directly attuned to this extreme risk. Sixty-four percent of those who answered the question indicated that they did know someone who died en route to the USA.

To summarize, we found our interviewees to be well informed about Border Patrol efforts; indeed, a large majority believed that it is much more difficult to surmount the obstacle course at the border. Moreover, a majority believe that it is much more dangerous to cross the border clandestinely today as compared with previous periods. Nevertheless, more than half (51%) reported that they were considering a journey north.

Although these perceptual factors are important, we also asked people with a previous migration history about their personal experience crossing the border. Perhaps direct experience is more important than perceptions. In our survey sample, 64% or 383 individuals indicated that they had migrated to the USA before (of these, 184 were undocumented). Of those who had previously migrated, we asked whether they were apprehended by the Border Patrol on their most recent trip to the border (Q62). Of the entire subset of people who had crossed before – with or without legal documents – 13% indicated that they had been caught by the Border Patrol; of only those individuals crossing without papers, 25% indicated that they had been caught trying to cross.7 We also asked whether the most recent trip to the USA was more difficult than they had anticipated versus less difficult/about the same (Q58). Twenty-two percent of experienced migrants reported that the crossing was harder than they had expected. Restricting this analysis to only those crossing without papers, 44% indicated that their journey was more difficult than expected.

These variables form the core of our analysis. In the regressions that follow we include these variables about potential migrants’ level of information about Border Patrol efforts, their perceptions of difficulty/danger in crossing the frontier, and in separate regressions restricted to experienced migrants, we include information about their past attempts at crossing. Summary statistics for each of these main independent variables, along with our main dependent variable of interest are presented in Table 1.

Table 1.  Summary of key variables
  • Includes legal migrants.

Considering to migrate (dependent variable)No (49%); Yes (51%)
Information about border enforcementNone (28%); Informed (72%)
Difficulty evading Border PatrolNot at all (6%); Somewhat (23%); Much more (66%); Impossible (5%)
Perception of dangerNot at all or somewhat (20%); Very dangerous (80%)
Knows someone who diedNo (36%); Yes (64%)
Caught on prior attemptNo (87%); Yes (13%)
Prior attempt more difficultNo (78%); Yes (22%)

We also include several control variables in the analysis. Much of the published work suggests that the typical Mexican migrant to the USA is a working age man.8 Therefore we include a dichotomous variable for sex (female, 1), along with age and age squared to account for a parabolic relation between age and propensity to migrate (the very young and the elderly are less likely to migrate). We include additional demographic controls for marital status (married, 1) as well as the number of children the respondent has. We also include a pair of controls for the respondent’s economic status. Whereas we lack wage data for our individual respondents, we include a subjective self-assessment of economic status in which people were asked to rate their economic welfare on a scale from 1 to 10. We also include a variable for the number of years of schooling the respondent has completed; while education may have an independent effect on the propensity to migrate, education is also expected to be highly related to one’s income. In addition, because there may be unique characteristics of the two towns represented in our study that are not included in the statistical model, we include a “fixed effect” term for the town itself in the form of a dummy variable for “Las Animas”. Finally, when restricting our models to the subset of respondents who had migrated before, we include a dichotomous variable for the person’s legal status (documented, 1; undocumented, 0).

Because our dependent variable is dichotomous, we run our models using a logit estimator with robust standard errors. Because several of our independent variables may be highly correlated with each other, we include them sequentially before presenting a model in which all are included. Additional diagnostic testing shows that multicollinearity does not present a significant problem.9 Our most correlated variables (danger crossing and difficulty evading the Border Patrol) were only correlated at the 0.27 level.

We acknowledge that our survey design may suffer from a particular type of response bias, but we can anticipate the direction of this bias. By conducting our interviews in Mexico, our survey does not include people who have already migrated, did not return to their hometowns during the fieldwork (which was timed to coincide with the towns’ annual fiestas), and therefore were not available to be interviewed. Thus, the sample may overrepresent people who stayed in Mexico and underrepresent people who had left. Clearly, undocumented migrants who were in the USA at the time of the survey were not deterred from migrating. Therefore, if there is a deterrent effect, we are more likely to detect it among those who have been successfully dissuaded by border enforcement efforts. This suggests that our results should indicate something of a bias in favor of a finding that the deterrence strategy has been successful. As we find little evidence of deterrence, this type of response bias is not cause for major concern.


Table 2 presents the results of the logit models. In model 1, we include only our demographic and economic control variables. This model confirms the expectation that migrants are more likely to be men of working age. The coefficient for gender is negative and significant, indicating that women are less likely than men to cross, and the parabolic age and age-squared terms indicate that the very young and very old are least likely to attempt a crossing. Interestingly, marital status and number of children do not have a statistically significant effect on the probability of migrating. We also find that people who report a higher economic status are more likely to migrate. We suspect that this may be because such persons have better means to migrate – for example, paying smuggler’s fees or obtaining legal documents – and/or because of possible reverse causation. People who have migrated in the past may have earned money in the USA to support their current lifestyle and are now considering a repeat visit. Level of education, as our models show, does not have a statistically significant influence on migration propensities.

Table 2.  Logit models: Migration decisions and perceptions of border crossing difficulty/danger
 1. Coef. (SE)P-value2. Coef. (SE)P-value3. Coef. (SE)P-value4. Coef. (SE)P-value5. Coef. (SE)P-value6. Coef. (SE)P-value
  1. Coef., coefficient; SE, standard error.

Border Patrol Difficulty−0.027 (0.150)0.8580.023 (0.156)0.881
Border Patrol Info0.552 (0.210)0.0090.472 (0.235)0.045
Danger−0.121 (0.234)0.606−0.237 (0.280)0.396
Death0.954 (0.269)0.0000.964 (0.309)0.002
Gender−0.895 (0.221)0.000−0.788 (0.235)0.001−0.887 (0.224)0.000−0.848 (0.223)0.000−0.909 (0.225)0.000−0.751 (0.247)0.002
Age0.106 (0.041)0.0100.113 (0.043)0.0090.102 (0.042)0.0150.106 (0.041)0.0100.102 (0.041)0.0130.101 (0.044)0.022
Age squared−0.002 (0.001)0.002−0.002 (0.001)0.002−0.002 (0.001)0.003−0.002 (0.001)0.002−0.002 (0.001)0.003−0.002 (0.001)0.005
Marital Status−0.058 (0.255)0.821−0.036 (0.271)0.894−0.086 (0.258)0.739−0.046 (0.258)0.859−0.165 (0.257)0.522−0.113 (0.279)0.686
Number of Children0.003 (0.051)0.960−0.002 (0.054)0.9730.005 (0.051)0.9150.003 (0.051)0.961−0.008 (0.049)0.870−0.008 (0.053)0.884
Economic Ladder0.131 (0.043)0.0020.126 (0.046)0.0060.141 (0.044)0.0010.136 (0.043)0.0010.137 (0.044)0.0020.147 (0.048)0.002
Education0.052 (0.035)0.1330.052 (0.037)0.1550.049 (0.036)0.1720.053 (0.035)0.1270.048 (0.035)0.1750.049 (0.038)0.198
Pueblo−0.700 (0.209)0.001−0.623 (0.221)0.005−0.726 (0.211)0.001−0.686 (0.210)0.001−0.023 (0.283)0.9340.052 (0.314)0.868
Constant−0.365 (0.858)0.671−0.579 (1.016)0.569−1.233 (0.916)0.178−0.404 (0.869)0.642−1.709 (0.949)0.072−2.749 (1.207)0.023

Models 2–5 sequentially include our main variables of interest. Contrary to the deterrence hypothesis, we find in models 2 and 4 that perceived difficulty evading the border patrol and danger in crossing – although signed negatively – do not have a statistically significant effect on migration decisions. Even more damaging to the deterrence hypothesis, in model 3 we find that individuals who report being well-informed about current Border Patrol efforts are more likely to cross. Additionally, model 5 shows that people who know of someone who died while attempting to cross the border are also more likely to migrate. We believe this result can be easily explained. Persons considering migrating are likely to actively seek information about Border Patrol operations to avoid apprehension. Knowledge of enhanced enforcement is not deterring these people, but is instead leading them to devise better evasion strategies. Moreover, we would expect those planning to go north to have many experienced migrants in their network of friends and family; therefore, they are more likely to know of someone who died while trying to enter the USA. Whereas the risk of death is very real, with thousands of successful crossings being made each day, border-wide, prospective migrants view the probability of dying to be acceptably low. Model 6 includes all of these variables in a single regression and comes to a similar conclusion.10

In Table 3, we restrict the analysis to those migrants who have crossed before. Perhaps perceptions of danger or difficulty are not sufficient; actual experiences in previous crossing attempts may be a more potent deterrent. In these models we also include a control variable for previous crossing with legal documents; not surprisingly, people who were able to enter the USA legally in the past are much more likely to cross. Interestingly, in these models we find that marital status is now statistically significant, with married people being less likely to migrate again. Economic status is no longer significant although we note a moderate degree of correlation between this variable and legal status.

Table 3.  Migration decisions among experienced migrants
 7. Coef. (SE)P-value8. Coef. (SE)P-value
  1. Coef., coefficient; SE, standard error.

Caught−0.622 (0.375)0.097
Difficult crossing−0.010 (0.357)0.977
Legal migrant1.663 (0.323)0.0001.866 (0.336)0.000
Gender−0.592 (0.372)0.111−0.601 (0.377)0.111
Age0.081 (0.078)0.3000.087 (0.078)0.269
Age squared−0.002 (0.001)0.061−0.002 (0.001)0.051
Marital status−0.947 (0.379)0.012−0.916 (0.383)0.017
No. children0.049 (0.062)0.4300.048 (0.064)0.449
Economic ladder0.051 (0.058)0.3780.058 (0.059)0.324
Education−0.024 (0.049)0.626−0.023 (0.050)0.641
Pueblo−0.374 (0.285)0.190−0.274 (0.294)0.351
Constant1.234 (1.680)0.4620.806 (1.668)0.629

Model 7 shows that people who report having been caught in the past are somewhat less likely to indicate an intention to migrate again in 2005. Although this provides some evidence of a deterrent effect, the result barely reaches statistical significance at the 0.1 level. To get a sense of the substantive impact of this effect, we compute predicted probabilities based upon these estimates by setting all dichotomous variables to zero and all continuous variables to their means. Changing the “caught” variable from zero (not caught) to one (caught) reduces the expected probability of migrating by roughly 8%. To put this in context, our models also show that women are 10% less likely to migrate than men and that married people are 17% less likely to migrate to the USA than singles. Therefore, the influence of border enforcement is substantively small compared to other factors. Model 8 includes our variable for experience of difficulty during crossing. Although this variable has a negative sign, we do not find a statistically significant effect.


The main justification for the strategy of border control implemented by the USA since 1993 was that it would deter undocumented migration at the source, in Mexico and other migrant-sending countries. Although higher wages and abundant job opportunities in the USA constitute powerful economic incentives, a robust border enforcement strategy was expected to limit access to the US labor market, making unauthorized migration less attractive. Whereas our research design does not enable us to compare migration propensities before and after new border controls were introduced, our results suggest that perceptions of the danger and difficultly involved in clandestine crossings have not discouraged migrants from attempting them. Political restrictions on immigration are far outweighed by economic and family-related incentives to migrate.

Our survey and qualitative research in Mexican migrant-sending communities in 2005–2006 indicates that migration strategies have been affected by enhanced border security. For example, border-crossing points have changed, the use of people-smugglers continues to increase, and unauthorized migrants are now more likely to seek entry through legal ports of entry. But few potential migrants are staying home primarily as a consequence of US border enforcement efforts. We also find that migrants who do go to the border have an extremely high rate of success if they persist. Among migrants interviewed in our 2005 survey, 92% of those who were apprehended at least once on their most recent trip to the border eventually were able to gain entry, without returning to their place of origin (Cornelius & Lewis 2006, p. 65). Among those interviewed in our 2006 survey, conducted in a rural community in the state of Yucatán, 97% of those apprehended on their most recent trip were able to enter successfully on the second or third try (Cornelius et al. 2007, Ch. 5).

From a policy standpoint, our findings suggest that current US immigration control policy is fundamentally flawed. The stated aim of reducing the flow and stock of unauthorized immigrants through a robust deterrence strategy has not been achieved. Ignoring this policy failure, in September 2006 the US Congress passed an immigration control bill that focuses exclusively on border enforcement – particularly the construction of new fencing and installation of high-tech detection hardware along 700 miles of the US–Mexico border – without addressing the root causes of migration. But additional investment of taxpayer dollars in a border enforcement-centered strategy of immigration control, leaving intact the employer demand for unauthorized immigrant labor, is unlikely to create an effective deterrent to unauthorized migration. An alternative approach, that is, increasing legal entry opportunities for low-skilled foreign workers through a guestworker program and/or providing a larger number of permanent, employment-based visas for such workers, would have a higher probability of success. By bringing the supply and demand for immigrant labor into equilibrium, the incentives for undocumented migration – essentially a black market for labor – would largely disappear.


The authors are indebted to Frank Bean and to anonymous reviewers for helpful comments on an earlier version of this article.


  • 1

    Of course, there may be a large difference between what the state is “willing” to do versus what it is “able” to do. Even if a state could, in principle, seal its borders to undocumented entry, it may not be willing to bear the economic, political, and diplomatic costs of doing so.

  • 2

    Bean and Lowell (2007) find a significant reduction in the average number of migrant apprehensions per Border Patrol agent during the post-1993 era of stronger enforcement, which they interpret as evidence of successful deterrence of clandestine entries. However, they also note the robust growth of the stock of unauthorized migrants living in the USA during the same period. They suggest that a substantial part of the increase is because of undocumented migrants staying longer in the USA as a consequence of tighter border controls, along with a strong US economy and weakness in the Mexican economy.

  • 3

    Whereas this discussion focuses on labor migration, states also work to restrict the entry of other forms of migrants. Fraudulent asylum seekers, criminals, terrorists, and culturally unwelcome foreigners (to name a few) have also been the subject of immigration restrictions.

  • 4

    The available evidence suggests that, at least initially, the additional obstacles to illegal entry in urbanized areas dried up migrant traffic within these areas, but had no effect on long-distance migrants, who detoured around them and began crossing in undeveloped areas. See, for example, Bean et al. (1994). In the fall of 2005, unauthorized entries began shifting back toward cities like San Diego, as migrants and people-smugglers found new modes of entry (e.g. using false or borrowed documents to enter through legal ports of entry).

  • 5

    For wording of the questions used in this analysis, see the Appendix.

  • 6

    This corresponds to 19% (55/284) of those who responded with a “no” to Q71.

  • 7

    Interestingly, only 23% of undocumented migrants who reported crossing the border during the period of tighter border enforcement since 1993 reported having been caught even once by the Border Patrol. This indicates that even with tighter border enforcement, the vast majority of unauthorized migrants are able to cross without ever being detected.

  • 8

    Whereas Mexican men continue to have a higher probability of migration, the proportion of women in the Mexico-to-USA flow has risen substantially in recent decades. See Cornelius and Lewis (2006, Ch. 6); Donato and Patterson (2004).

  • 9

    In particular, the variance inflation factor scores for a linear model were obtained.

  • 10

    In another regression, not shown, we estimate this model with an additional control for documented status (dichotomous, previously migrated to the USA with legal documents equals one, zero otherwise). Our results do not change significantly with this additional control.


Translations of principal questionnaire items used in data analysis

  • 58Was your experience of crossing the border what you had expected before leaving (Tlacuitapa/Las Animas)? Was it easier, or more difficult?
  • 62While attempting to cross the border, did you suffer some type of physical harm?
  • 71Have you thought about going to the USA to work in the current year?
  • 77If you don’t think you will go north this year, why not?
  • 78Do you know something, or have heard something, about the efforts of the Border Patrol to make it more difficult for undocumented migrants to cross through San Diego, Arizona, and some places in Texas?
  • 80How difficult is it to evade the Border Patrol while crossing the border these days?
  • 84Currently, how dangerous is it to cross the border, if you don’t have papers?
  • 85Do you know someone who went to the USA but who died in the desert or the mountains, while attempting to cross the border?
  • 130Here we have a ladder with 10 steps (show picture). On step number “10” is a family with the best living conditions in this town at present. On step number “1” is the family with the worst living conditions. On what step would you locate yourself and your family?