The spatial ecology of alcohol problems: niche theory and assortative drinking

Authors


Paul J. Gruenewald, Prevention Research Center, Pacific Institute for Research and Evaluation, 1995 University Avenue, Ste. 450, Berkeley, CA 94704, USA. E-mail: paul@prev.org

ABSTRACT

Aims  This paper summarizes several theoretical perspectives that serve to explain observed associations between concentrations of alcohol outlets and alcohol-related problems. A critique of each perspective discusses how each addresses the social etiology of these problems; that is, how, where and why these problems arise in association with alcohol outlets?

Methods  This theoretical work is based upon mathematical and computational models of the ecology of alcohol-related problems developed in the ‘Ecosystems Modeling Project’, an advanced research project of the National Institute on Alcohol Abuse and Alcoholism, United States.

Results  Associations between outlets and problems are thought to arise from the concentration of individuals in drinking places (‘flow models’), the attraction of some places for people at risk for problems (‘gravity models’), or because outlets are located in high-risk neighborhoods and have negative social normative effects (‘social contextual models’). None of these approaches explain how some outlets come to have more problems than others (e.g. violent outlets). An alternative social ecological model is introduced which asserts that the complementary processes of niche marketing and assortative drinking form the social dynamic that explains these relationships. Alcohol sellers ‘niche market’ to select social strata, drinkers return to establishments at which they find people like themselves, and consequent social stratification of the market-place increases the levels of related problems in some outlets.

Conclusions  The proposed mechanism is very general, and suggests that over-concentrations of outlets will lead to stratification of drinking groups and intensification of problems related to those outlets.

INTRODUCTION: ECOLOGICAL STATISTICS OF ALCOHOL OUTLETS AND RELATED PROBLEMS

During the past five decades there has been a dramatic growth of research directed at the roles alcohol outlets play in producing or aggravating alcohol-related problems. Although the idea that alcohol outlets, particularly the local bar or pub, can be a source of social problems is often anathema to commercial interests [1], on the whole, and for reasons not well understood, an array of problem behaviors correlate persistently with numbers of outlets in community areas. These associations are well summarized in recent publications on alcohol problems [2], policies [3] and prevention [4]. Most well-studied among the various problems associated with alcohol outlets are violent assaults, drunken driving and motor vehicle crashes [5]. However, it also appears that pedestrian injury collisions [6], intimate partner violence [7,8], child abuse and neglect [9], sexually transmitted disease [10] and access to alcohol among both college students [11] and youth [12,13] are correlated with densities of alcohol outlets across community areas. Because the vast majority of these studies are cross-sectional in design, it is difficult to assign causal status to outlets in these circumstances. Nevertheless, there is ample reason for researchers and policy makers to be concerned about the roles that outlets play in generating, supporting or aggravating community problems.

Because alcohol outlets are environmental features of communities that expose populations to opportunities to drink and socially model others' drinking behaviors, mostresearch in this area consists of population studies that relate observed rates of problem outcomes to differential exposures to neighborhood conditions. The confounders considered in these studies include most of those proposed in contemporary social theories: characteristics of populations and neighborhoods that reflect social capital [14], neighborhood disorder (or incivility) [15] and disorganization [16]. The list of suspected confounders also includes other, more mundane, environmental features of community settings that, in fact, turn out to matter a great deal to alcohol problems; these include patterns of traffic flow [17] and densities of other retail establishments (e.g. as counterfactuals) [18]. Finally, after some years of effort, statistical issues that arise in analyses of these intrinsically spatial data are being addressed [19], and longitudinal data sets are enabling researchers to examine these relationships over time [10,20–22]. Despite these achievements, the results of these studies continue to be open to interpretation as ecological fallacies can arise at any point [23]. For example, an alcohol-related crash attributed to a nearby outlet could, in fact, be related to drinking in an outlet much further away, or to drinking in some other venue. There is much room for empirical refinement among these studies and sound scientific judgement calls for a focus upon specific predictions from theoretical models when analyzing these data.

All this said, theorists interested in the ecology of social problems in general, and social problems related to alcohol outlets in particular, acknowledge that some social mechanisms must relate the ways in which drinkers use alcohol outlets to problems that are seen around those outlets at the population level. Individual patterns of drinking and related human behaviors must aggregate in specific ways over time and space to create the distributions of problems seen across communities. In the parlance of ‘middle-level social theorists’[24,25], the micromotives and behaviors of individuals aggregate to form the behaviors of groups that, in turn, affect the subsequent motives and behaviors of the individuals themselves [26,27]. This micro–macro dynamic forms the middle-level theory that is essential to, and at this point absent from, ecological studies of alcohol problems. Theoretical arguments developed solely at the population level about the roles of social capital, social disorganization and alcohol outlets in alcohol-related problems [18] are limited to the extent that they do not address the dynamic social processes that shape the distributions of these problems across communities.

The interests of this article are to offer some comments on these theoretical issues with respect to alcohol studies and propose a parsimonious conceptual model of the social ecology of alcohol use that will fill this gap. In considering the two problems most studied with regard to alcohol outlets, violent assaults and drunken driving crashes, we can ask two focused questions: (1) ‘what are the social mechanisms that cause greater numbers of violent assaults to occur near bars or taverns’ and (2) ‘what are the social mechanisms that account for the spatial distributions of alcohol-related crashes in our communities?’. To some extent what is at issue here is the nature of social theory as it applies to explaining problems related to alcohol outlets. It is not sufficient to observe that, because problems are related to these outlets and people use these outlets in different measurable ways, these relationships are ‘explained’. Instead the important question is to ask how these relationships arise in the first place, and to identify the social mechanisms that support the emergence of these relationships in community settings. With this in mind, this paper provides a brief overview of current approaches to understanding the outlet–violence relationship, followed by the introduction of a micro–macro approach to elucidating the social mechanisms that shape the use of different drinking contexts. This approach will help us to understand the emergence of drinking problems as they relate to the human use of drinking contexts, explaining, for example, how it comes to be that greater numbers of bars are related to greater numbers of problems, and why some bars come to have more problems than others. As will be seen below, the focus on bars and taverns is something of a convenience. The arguments presented here can be extended to other drinking venues.

WHY DO OUTLET DENSITIES MATTER?

In a tradition not entirely unique to this literature, ecological studies of alcohol outlets and problems have not been burdened with much theoretical baggage over the past 30 years. The primary concern of researchers appears to have been the careful examination of the statistical facts of these relationships, not the development of suitable theory regarding how these relationships emerge in community settings. Perhaps the issue is viewed as too simple to warrant theoretical argument: One might simply reason that people drink at outlets and sometimes have problems, so outlets are related to problems. Making alcohol more available, drinkers will drink at these outlets more often (an observation dignified as ‘availability theory’) [5]. An alternative view of this history, however, is that alcohol researchers had to address a number of important epidemiological issues (noted above) before theoretical work could commence. Thus, while the published literature provides a few hints about the social mechanisms that relate outlets to problem outcomes, a comprehensive theory of the etiology of problems related to alcohol outlets is yet to emerge. Aside from noting that greater alcohol availability appears to lead to greater use and problems, three kinds of general mechanisms are either proposed explicitly or suggested by empirical work in the area, namely ‘flow models’, ‘gravity models’ and ‘social contextual models’ of outlets and problems.

Flow models

The simplest approach to understanding outlet effects is to assume that greater numbers of outlets are used by greater numbers of drinkers and this leads to the concentration of problems around dense outcrops of outlets in community neighborhoods. Greater numbers of outlets capture a greater ‘market share’ of drinkers and the resultant flow of people through outlets is sufficient to explain the greater rates of violence and alcohol-related traffic crashes that occur in these areas. Although saying little more than that some proportion of drinkers are at risk for different problems (e.g. aggression or drunken driving) and drinkers are more likely to drink at outlets when outlets are available, this approach is sufficient to explain the general spatial signatures of many ecological analyses of violence and motor vehicle crashes. Greater numbers of outlets in an area should be related to greater throughput of customers, fixed proportions of these customers may interact in a violent manner or drive after drinking, and so greater prevalence of violent assaults and drunken driving crashes will appear. The early studies by Scribner and colleagues [28,29], that observed direct relationships between numbers of outlets and problems, and later work by Gruenewald and colleagues [17,30,31], that identified traffic flow patterns related to motor-vehicle crashes, support this view.

Gravity models

The assumption that drinkers are as likely to pick one outlet as another does not square well with the observation that drinking places are differentiated not just by their ‘throughput’ or ‘flow’ but also by the character of the customers who frequent these establishments. For example, not only are there ‘violent’ bars, there are ‘violent’ bars on the same streets where other not-so-violent bars, taverns and pubs appear [32,33]. So simple flow models may be supplemented by the assumption that certain outlets selectively attract certain clientele, perhaps those who are more disposed to violence than others [34,35]. These ‘attractors’ would add unique risks to particular community settings when at-risk populations (e.g. young males) are attracted to specific establishments. The social mixing and drinking of these populations in these places can exacerbate further the risks for problem outcomes [36,37]. One would expect from these models that some outlets would have far greater numbers of problems than others and that these outlets might exhibit unique ‘markers’ of this status reflecting characteristics of their clientele (e.g. signage, lighting, etc.), as indeed they do [38].

Social contextual models

The approach of flow models is to assume that community populations use available outlets and, consequently, the more outlets there are in an area the more problems will occur. Gravity models refine this approach by noting that some outlets acquire characteristics that attract specific at-risk clientele and these drinkers exhibit more problems at those establishments. In contrast to these two very practical ways of understanding problems associated with alcohol outlets, other researchers note that these establishments are often found in neighborhoods already at risk for many problems, poor minority neighborhoods in downtown areas of urban environments [39]. Thus, from the perspective of social disorganization theory, alcohol outlets are seen as one among many markers of neighborhood disorder related to lax normative constraints against problem behaviors. All else being equal, residents of neighborhoods with many outlets will perceive greater levels of disorder [40], and these signs of disorder will be related to greater levels of incivility, lower collective efficacy [41] and greater numbers of problems [42].

Although the predictions of social disorganization theorists are supported whenever they are tested in ecological studies of outlets and problems, it is also the case that unique effects related to alcohol outlets continue to be observed. Measures of social disorganization matter a great deal to the prevalence of violence across neighborhoods [18] and within neighborhoods over time [21]. Apart from these measures, however, the numbers and densities of specific outlets, such as bars, continue to present independent risks for violence, have a greater impact on violence in socially disorganized neighborhoods than in others [18] and affect violence rates in surrounding areas of communities independent of local population characteristics [21]. These observations do not necessarily contradict the predictions of social disorganization theorists. For example, it could be argued that the presence of many bars in a neighborhood remains a sign of social disorder and that greater numbers of bars have a stronger relationship to perceived disorder in ‘stigmatized’ places [40]. They do, however, suggest that independent outlet effects can be detected whenever researchers take the time to look. More important from a theoretical point of view is the observation that these different arguments exhibit the two contrasting views of outlet effects that dominate the research literature; either alcohol outlets provide specific opportunities for violence related to the use of drinking places (a purely social ecological effect), or they are one of many environmental influences on social normative processes that affect problem outcomes (a social normative effect).

TOWARDS A SOCIAL ECOLOGICAL THEORY OF OUTLETS AND ALCOHOL PROBLEMS

Admittedly, the contrast of social contextual models, as labeled here, with social ecological approaches, as introduced, is artificial. It is likely that an excess of alcohol outlets in a neighborhood will influence community perceptions of neighborhood conditions and provide opportunities for at-risk populations to mix in potentially troublesome circumstances. The theoretical challenge is not to establish which of these two approaches matters most or least, but rather how these approaches can be integrated towards the goal of explaining the etiology of community problems related to alcohol. This challenge can be addressed by (a) elucidating the social roles played by alcohol outlets in drinking and alcohol-related problems and (b) identifying the roles alcohol outlets play in larger community systems related to the production and distribution of alcohol in community settings [43].

Alcohol outlets, like credit cards, are among that unique set of physical objects that have substantive social meaning and play a variety of different social roles in communities [44]. Rather than a medium of economic exchange, however, alcohol outlets are places of economic and social exchange that affect and are affected by the social conditions of the neighborhoods in which they are located. This being the case, it is essential to understand how different social meanings accrue to alcohol outlets or, equivalently, elucidate the social mechanisms that establish the roles that alcohol outlets play in community settings. With this in mind, it is clear that availability theory, flow and gravity models and social contextual models provide only fragmented views of the larger social system in which drinking takes place.

The alternative social ecological model proposed here attempts to situate outlets with respect to their primary roles in community social systems. Outlets can be viewed as the connecting point, so to speak, between individuals' proclivities to use alcohol and commercial and social markets for alcohol in community settings. Central to this argument is the claim that drinkers exchange economic and social goods at outlets; they provide capital for the continuing operation of these outlets, and incidentally form social groups for drinking that can promote a number of different problem behaviors (exchange theory) [27,45]. In this view the microbehaviors of individual drinkers interact with social structures for the commercial distribution of alcohol to aggravate or mitigate problems related to alcohol use.

At this level of explanation the framework of middle level social theory can be applied to the elucidation of the social dynamics underlying these outcomes [46,47], partitioning the relevant theoretical issues into a suitable conceptual framework for modeling social problems [48]. This framework provides fundamental guidance to the development of any social ecological model of alcohol outlets and problems:

  • 1Agency: individual drinkers are agents who move through their environments and select social and physical contexts in which to drink.
  • 2Contexts: commercial establishments provide contexts for drinking and compete for market share among drinkers.
  • 3Contacts: drinkers contact one another within drinking contexts, influencing one another's behaviors in these contexts (e.g. through social imitation).
  • 4Topology: locations and times of use of drinking contexts are constrained by physical and social structures (e.g. alcohol control laws, social networks).

Considering each of these concepts in turn, outlet densities matter because greater numbers of outlets provide more opportunities for agents to make choices to drink in contexts that suit their drinking preferences (e.g. at a particular bar). Having selected common places to drink, contacts among at-risk populations place individuals at greater risk. If these outlets are spatially located within or near neighborhoods with larger at-risk populations, then these populations are more likely than not to use these local outlets for drinking (topology). Importantly, these conceptual arguments track well with the empirical work reviewed in previous sections of this paper.

One striking feature of these basic concepts for a social ecology of drinking is that each is either explicitly dynamic (agency and contacts) or provides a place or structure in which these dynamics will play out in a community (contexts and topology). Indeed, each represents either human activities (agency and contacts) or their interactions with the environments in which they live (contexts and topology) that serve as the foundation of ecological studies. However, this list of ideas does not constitute an adequate theoretical statement of the processes that enable alcohol problems to emerge in community settings. Although much can be said about the agency of drinkers, little has been said (or is ever said) about the agency of commercial alcohol establishments. Some core dynamic must drive the interrelated actions of individual drinkers and commercial agents, a dynamic that can provide insight into the expected developmental trajectory of a new alcohol market, a market that provides drinkers with the social and physical goods they desire through the competitive nature of the commercial alcohol enterprise.

NICHE THEORY

When looking at the different kinds of commercial alcohol establishments that operate within communities, one of the remarkable things about them is the relatively high degree of diversity in outlet characteristics and clientele that exists among these different drinking places. As examples, some bars cater to youthful crowds, others to older middle-class male drinkers and some to those drinkers wedded to ‘eye-openers’ every morning; some others present country music, some have sawdust on the floor, yet others sport bright interiors, and so on. Standing back a little from these settings, we might ask where all this diversity comes from? One answer provided by theories of competitive advantage [49] and marketing models in economics [50] is that markets diversify in response to different aspects of consumer demand. Markets, and the goods sold in those markets, diversify in correspondence to differentiated demand among consumers [51]; market segmentation can result and niche markets can form. Market segmentation helps to ensure a steady stream of profits to commercial interests working within those segments while simultaneously minimizing competition between segments. Thus alcohol markets may segment with respect to quality (e.g. broadly sold brands versus craft beers) [52], present different images (e.g. macho versus appeal to elites) and form niche categories so small as to be best served by specific commercial retailers (e.g. local independent brewers). Brought to its logical conclusion, efforts at niche marketing can support commercial interests that address the unique needs of very narrow classes of consumer [53] and can lead to market discrimination, as some consumers are excluded from certain markets [54].

Alcohol outlets, of course, have been serving the drinking needs of specific market segments for some time. Retail establishments compete for drinkers and offer differentiated forms of entertainment to attract specific segments of the alcohol market (e.g. country music, rock-and-roll, or no music at all). What has not been recognized in the alcohol literature to this point in time, however, is that this dynamic process induces levels of market segmentation that can serve to concentrate at-risk users in specific outlets. Thus, the attractiveness of different bars to consumers is a function of market segmentation intended to maximize returns on investment by alcohol retailers. The result, predictable from economic models of market competition, is the progressive stratification of consumers across outlets as growing numbers of outlets in a community compete with one another for market share. If some aspects of the dimensions on which segmentation takes place are correlated with risks for problem outcomes (e.g. age, drinking patterns, predispositions to aggression), problems related to these risks (e.g. drinking and driving, violence) will become correlated with the locations of these outlets.

ASSORTATIVE DRINKING

The primary reason why commercial markets segment along different lines is that consumers themselves have different preferences for different kinds of the same good and these become expressed when these differentiated goods become available [55]. If only one kind of alcoholic beverage was available, drinkers would all purchase that one beverage. However, because alcoholic beverages come in at least three basic types (beer, wine and spirits) and preferences for those types tend to be somewhat exclusive, markets tend to segment along those lines (e.g. wine bars). Consumers' preferences exist, in a sense, prior to their identification by commercial interests. The problem for commercial interests is to identify those preferences and market to them. The challenge for consumers is to recognize their own preferences with regard to the options confronting them in the market [53] and select contexts with regard to these preferences (e.g. selection by consequence) [56]. How consumers go about recognizing their own preferences for goods is a very complex cognitive process; nevertheless, it is clear that these choices are being made with regard to alcohol outlets. The empirical observations with regard to these choices demonstrate systematic and strong differences in the selection of preferred drinking venues between demographic and drinking groups [57], with heavier drinkers biased toward drinking outside the home [58]. Beyond these observations, however, personal reflections on the use of places for drinking are also compelling. The person drinking at a country music bar on Friday night is not likely to be found in a jazz bar on Saturday. Conversations over beer at the local pub are unlikely to be repeated by the same people later in the evening at the wine bar. The demographic groups and types of drinkers frequenting these establishments are very distinct.

This observation leads to a statement of a central social process that may explain much about the role that drinkers play in shaping their drinking environments, namely assortative drinking. One of the particular characteristics of alcohol establishments that attracts specific demographic or drinking groups is the nature of their clientele. Not only do the clientele of many establishments arrive in small groups of two or more, usually themselves related closely by demographic characteristics, but common demographic groups (e.g. young males) would appear to attract one another to the same establishments [38]. In the absence of other bases upon which to make choices of places to drink, the tendency towards homophily among drinkers will encourage stratification of customers across different outlets. This is the same process that has been identified in macro-sociology as supporting racial segregation [26,59], but can also be recognized in the small group dynamics of friendship networks [60] and concordant drinking among married couples [61]. The implications of this observation become more pointed when it is observed that other, less prosocial, characteristics of drinkers also tend to assort across drinking places (e.g. hostility, aggression and heavy drinking) [58,62,63].

As this final argument suggests, the characteristics of drinking establishments are not determined simply by marketing decisions, but also by the character of the clientele who frequent those places. Thus, two reciprocal social processes relate one to the other and, as consumers select places that conform with their expectations about drinking, those drinking places adapt their services to meet the needs of consumers who come through the door. The goal of the consumer is to maximize returns on the investment in drinking as a form of entertainment; for the commercial operator the goal is to maximize and ensure returns on investment in the alcohol establishment.

Figure 1 presents an outline of the complementary core dynamics that, according to this approach, underlie the social ecology of drinking problems. This representation assumes that drinkers' primary interests with regard to alcohol are basic, namely the beneficial effects that drinkers' experience from alcohol use and the social camaraderie of drinking groups (sociality). It also assumes that commercial interests can benefit from marketing alcohol to drinkers by providing them with contexts in which drinking is both enjoyable and inexpensive. The interests of these commercial enterprises are simplified to raising economic capital and minimizing legal exposures and risks related to operations at alcohol establishments. Clearly, many other benefits and constraints are operative in the case of both drinkers and commercial establishments. As the arrows in the figure indicate, drinkers provide a demand for alcohol (‘drinking’) that is met by commercial interests (‘alcohol sales’). Drinking and sales are correlated with problems related to alcohol use. It is the existence of these problems that regulates further drinking and the activities of commercial establishments selling alcohol. In the case of drinkers, these could simply be problems related to alcohol (e.g. hangovers). In the case of commercial interests, different problems arise (e.g. public drunkenness), and these might lead regulatory interests to act to further constrain commercial activities. Regardless, in this approach the demand for alcohol is met with supply and comes to equilibrium at a point which satisfies the interests of both consumers and suppliers.

Figure 1.

Niche theory and assortative drinking model of alcohol use

SUMMARY AND IMPLICATIONS

The conceptual outline of the model presented in Fig. 1 shows that two complementary dynamics relate consumer and commercial interests in the alcohol market. The interests of consumers are to obtain and use alcohol in enjoyable circumstances. The interests of commercial enterprises are to sell alcohol and provide enjoyable circumstances for drinking. The two dynamics form a positive feedback loop (lower portion of figure) in which the interests of consumers reinforce the activities of the commercial market, and the activities of the commercial market reinforce alcohol use among consumers. Without any other constraints on this dynamic system, the result will be (1) the progressive diversification of the drinking market to address the different demands of consumers and (2) greater use of alcohol as consumers' specific demands for alcohol are met in more efficient ways. Commercial interests will progressively segment the market creating unique niches for drinking. Consumers will assort themselves across these niches, forming drinking subgroups.

The mutually co-adaptive dynamics suggested by this model lead to a number of different implications for alcohol markets and policy makers' efforts to reduce problems related to alcohol in community settings. The first major implication, of course, is that alcohol markets diversify with increased numbers of alcohol outlets. A minimum number of consumers is necessary to sustain a profitable alcohol outlet, and it is competition among commercial outlets that leads to diversification and the development of niche markets. Consequently, all else being equal, greater numbers of alcohol outlets in suburban and urban settings will be related to greater diversity among those outlets and a greater degree of social stratification among drinkers. This suggests that, in general, within urban areas niche marketing and assortative drinking will lead to the further stratification of drinkers across outlets and the creation of problem ‘hot spots’; that is, places in which the rate of a problem outcome is excessively high. The model suggests that these ‘hot spots’ should increase in intensity as stratifying processes progress to assort more finely drinkers of all types, including problem drinkers of varying types, into specific outlets. The tendency for homophily among drinkers should lead to the clustering of different drinker ‘types’ across establishments as clientele assort themselves with respect to outlets, and the degree of clustering will be directly proportional to the number of different kinds of outlets available.

As suggested by this model, the contribution of a new alcohol outlet to alcohol problems in a community will be achieved through two processes, the increase in numbers of consumers using the outlet and the further stratification of the drinking population. Considering these two possible effects, it is important to note that an outlet need not increase number of drinkers or drinking levels in a population in order to increase numbers of drinking problems. The social stratification of drinking groups that is effected by the addition of an outlet to a place can be sufficient to do so. The provision of one additional outlet to an area might have little impact on the overall availability of alcohol (availability theory), but have a substantial impact upon stratification processes (social ecological theory). Viewed from this perspective the impact of one or two additional alcohol outlets to a neighborhood with a high degree of social disorganization could result in further stratification of drinking groups and an increase in at-risk drinking among subgroups of drinkers. This prediction of the model has strong implications for the prevention of alcohol-related problems in community settings. The stratification induced with the addition of alcohol outlets to one area of a community may act as a catalyst for problems, effecting a phase transition in risk levels in which a constant level of drinking is related to greater numbers of problems (e.g. explaining the minority paradox) [64,65]. Such phase transitions are suggested by preliminary mathematical ecological models of alcohol outlets and problems [66], and should be detectable through statistical analyses of outlets and patron characteristics that focus upon their mutually related assortative characteristics [67]. Importantly, the degree to which these effects are observed should be related to the risk characteristics of local populations (social normative theory), the demographic sources of stratifying subpopulations and the number of alcohol establishments which must compete among themselves for consumers.

The second major implication of the proposed model for the prevention of alcohol-related problems in community settings is that the same process that leads to the stratification of drinking subpopulations can also lead to the shielding of drinkers from preventive interventions. Niche marketing and assortative drinking processes will lead to the stratification of drinking subgroups, subgroups that are mutually supportive and share particular norms. Some of these norms may be quite nugatory; for example, use of alcohol as an ‘eye-opener’ for breakfast, support for the belief that driving after drinking is acceptable, and the value of competitive drinking games as a form of entertainment. As argued here, greater numbers of alcohol outlets will enable these subgroups to cluster in the population, providing them with venues for drinking. This process will make it much more difficult to prevent these problems as drinkers provide one another with mutual supports for problem behaviors in these contexts. It will also make it much more difficult to successfully treat populations of alcohol-dependent individuals when drinkers return to these highly stratified social contexts after treatment [68,69]. Again, the stratification of drinkers across contexts, not the addition of drinkers or greater levels of drinking per se, will be the driving force behind these issues.

Finally, as noted briefly above, the choice to focus upon formal establishments for the sale of alcohol should be recognized as a convenience to the current stage of model development. As proposed here, the niche theory and assortative drinking hypotheses can be applied to any drinking venue, whether commercial or social. In the case of social hosts the profit is not made in economic terms, but rather in terms of social capital, such as successful parties that enhance social ties. Although from the point of view of public policy such venues for drinking cannot be easily regulated, the incidence of such venues is an important component of any adequate theory of the social ecology of alcohol use. In principle, the same effects observed for commercial venues should also be seen with regard to social venues, with the caveat that drinking parties are a movable feast of sorts, held at different places at different times. The major difference between the two types of venues is that commercial establishments must be profitable to remain in business and therefore have strong incentives to pursue stable niche markets. For this reason, social venues for drinking should not be expected to induce the high degree of market stratification that will result from the commercial institutionalization of alcohol markets. Social venues are, however, by their nature, socially stratified and, to the degree that alcohol is provided cheaply and in great amounts, might be very productive of alcohol-related problems. Regardless, the commercialization of alcohol distribution systems entails an extra cost to society, the indirect costs of efficient market systems that incidentally aggravate problems related to alcohol. To the that extent we can understand this ecological system, we can regulate it effectively to mitigate alcohol-related problems in our communities.

Acknowledgements

Research for and preparation of this manuscript were supported by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) Center grant no. P60-AA006282 and NIAAA Merit Award no. R37-AA12927. The development of the author's thinking about the ecology of alcohol outlets and drunken driving has been shaped by many influences. Of particular importance to the current work have been the many discussions with colleagues whose ecological inquiries were supported by NIAAA ADM Contract no. 1 AA 410012, the ‘Ecosystems Models of Alcohol Related Behavior’ project. The author is particularly indebted to the support provided by Drs Carlos Castillo-Chavez (Arizona State University, ASU), Dennis Gorman (Texas A&M), Priscilla Greenwood (ASU), Igor Mezic (University of California, Santa Barbara), Jadranka Mezic (AimDyn), Karen Peterson (NIAAA), Anna Tsao (NIAAA), Lance Waller (Emory University), Andrew Treno (Prevention Research Center) and Bridget Freisthler (University of California, Los Angeles). This paper could not have been completed without essential contributions from Dr Elizabeth A. LaScala.

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