Encyclopedia of SociologyVol._4

distribution of family income (the share of total income received by different families) was remarkably stable throughout the twentieth century despite tremendous growth in population and economic output and social upheavals such as the civil rights and women’s liberation movements. This stability suggests that the process governing the allocation of family income was nearly in equilibrium. The term ‘‘social change,’’ especially change seen as part of a unique historical process, usually is associated with change from one distinctive situation to another, very different situation. It implies the antithesis of social equilibrium. The way in which the social status of women and minorities has changed during the twentieth century exemplifies social disequilibrium.

Studies of social dynamics do not necessarily assume the existence of an equilibrium. This point is made clear by studies of the dynamics of economic growth, which often envision a process of never-ending expansion and improvement. Similarly, some dynamic processes imply not a steadystate condition but continual oscillation between conditions. A classic sociological example is Pareto’s (1935) analysis of the circulation of elites.

Fifth, the term ‘‘social dynamics’’ is almost always used in situations in which there is an interest in the process of change: the step-by-step sequence of causes and effects and the way in which intermediary changes unfold. It is rarely used when only a simple before–after comparison of the condition of the system is the object of interest. Instead, when authors use the term ‘‘social dynamics,’’ there is usually a sense that the details and sequencing of changes are important because changes are contingent: If the sequence had been interrupted or altered at an intermediary point, the final outcome might have been different. For example, models of social protest often recognize that the state’s response to protests may range from peaceful conciliation to violent suppression. The nature of the state’s response is an important contingency because it affects the likelihood, timing, and character of future protests.

Sometimes the sequence of changes occurs on the level of the system as a whole rather than on the level of individual members. For example, in a simple model of population growth, individuallevel changes are very elementary: birth followed by death, with the timing of the two being the only

question. On the population level, the addition and loss of individuals over time represent a sequence of changes even though on the individual level there may be few, if any intermediary changes and thus little sense of a sequence of causes and effects.

REASONS FOR STUDYING

SOCIAL DYNAMICS

What motivates sociological interest in social dynamics in general and dynamic models in particular? The most potent reason is the long-standing interest of sociologists in social change, coupled with an increasing recognition that a tremendous amount of scientific leverage can be gained from identifying regularities in patterns of change and then formulating sociological theories that explain them, that is, from studying social dynamics and not just unique historical events. Leverage comes not only from the increased richness of theories of social dynamics but also from greater methodological power in discriminating among competing explanations, as is indicated in more detail below.

As observers of the great social transformations of the nineteenth century, the founders of modern sociology (e.g., Marx, Spencer, and Weber) were keenly interested in social change. However, in the middle of the twentieth century, when structural functionalism and Parsonian thought were dominant, social change was regarded as a minor subfield of sociology. Interest in social change was renewed after a reawakened recognition of social conflict and the concomitant criticism of the assumption of social equilibrium in structural functional theories.

An accelerating pace of global change has added to this interest (Sassen 1988; Boli and Thomas 1997). Rapid growth of the world’s population; high levels of mobility of people, goods, and capital between and within nations; the transformation of agricultural societies to industrial and postindustrial societies; social upheavals ranging from strikes, to social protests, to revolutions, to wars; the creation of new organizational forms (e.g., holding companies, multinational corporations, international organizations); fundamental transformations of political regimes, including the failure of communist governments; steady increases in the number and volume of new technological innovations; depletion of natural resources; ex-

tinction of plant and animal species; and changes in climate induced by human activities are only a few of the world-level changes that make it virtually impossible for sociologists who study largescale social systems not to be interested in social change.

Although some scholars view many of these changes as historically unique, the concrete social and economic problems that result from them motivate attempts to find regular patterns and predict future changes, in short, to develop dynamic models of societal and global changes. Consider the massive changes in eastern European nations that began in the late 1980s. From the late 1940s to the late 1980s, those nations were governed by totalitarian polities and had commandtype socialist economies. Now most of them appear to be headed in the direction of market-type capitalist economies and democratic polities. The intellectual challenge, as well as a major problem for policymakers, is to develop a theory of the transition from one to the other, that is, a theory of the dynamics of the social change that is expected to occur. The fact that no satisfactory theory existed when the transition began was apparent to the general public as well as to social scientists. It points to the practical as well as scholarly value of studying social dynamics.

Sociologists who study micro-level phenomena (individuals and families) also cannot ignore social change. The life course of individuals in modern societies has a typical sequence of activities associated with aging (e.g., birth, day care, school, work, marriage, child rearing, retirement, death) that commands considerable attention by sociologists. Historical changes in family patterns (e.g., increases in premarital cohabitation, delays in marriage, changes in husband–wife roles, increases in divorce, baby booms and baby busts, increasing institutionalization of the elderly) also put social change at the forefront of the attention of sociologists who study the family. These subjects are perhaps more easily viewed in terms of social dynamics than are ones pertaining to global and societal changes because similar patterns across individuals and families are more readily apparent.

Sociologists who study behavior in small groups were among the earliest to express an interest in social dynamics. This interest received a major boost from Bales’s Interaction Process Analysis (1950).

Game theorists, who attempt to explain the moves and countermoves of actors in highly structured situations, also exemplify a concern with social dynamics in small groups, though they, much more than Bales and his intellectual descendants, concentrate on formal models and deemphasize hypothesis testing and empirical results (see Shubik 1982).

There are also metatheoretical and methodological reasons for studying social dynamics even when the primary intellectual concern is with statics, that is, with relationships among actors or variables at a single point in time.

First, studies of relationships at a single point in time implicitly assume a steady state or equilibrium. Otherwise relationships at a given time point must be transitory and in the process of changing, a situation that would degrade their potential contribution to enduring sociological knowledge. A steady state may or may not exist. If it does not exist, one needs to study social dynamics to understand relationships at a point in time. If a steady state does exist, much can be learned by studying social dynamics that cannot be learned easily by studying relationships at a single point in time. For one thing, two theories may imply the same relationship among variables at a given point in time but imply different time paths of change. In that case, a study of social dynamics can differentiate between them, whereas a study of the steady state cannot. For another thing, a theory of relationships at a point in time is invariably the special case of one or more theories of change over time, and the latter theories almost always have a richer set of implications than do the former. This means that in general there are more ways to test theories of social dynamics than to test theories of social statics.

THE NATURE OF DYNAMIC MODELS

As was noted earlier, developments in dynamic models (and derivative developments in methods of dynamic analysis) are the major commonality in sociological studies of social dynamics. To understand the main features of dynamic models, it is important to differentiate them from other types of models.

The most basic distinction is between static and dynamic models. Static models describe rela-

tionships among social actors in a system or among the attributes of a social entity at a given point in time. As was noted earlier, they implicitly assume a steady state or equilibrium, a phenomenon that is about as common in nature as a vacuum. In contrast, dynamic models describe the process or sequence of changes among actors in a social system or among the attributes of a social system.

Dynamic models also can be contrasted with comparative static models, which are especially common in economic analyses and analyses of social experiments. Although both deal with change over time, they differ in an important way. The process of change leading from conditions at the earlier time point to conditions at the later time point is fundamental to a dynamic model. In contrast, the change process is ignored in a comparative static model, which resembles a black box that relates conditions at one point in time to conditions at a later time.

To illustrate this distinction, consider alternative ways of explaining a son’s occupational prestige. In a comparative static model, the son’s prestige may be related to his father’s socioeconomic status and his own education without any attention being paid to the mechanisms and processes that lead from those background conditions to the son’s condition as an adult. In a dynamic model, the father’s socioeconomic status and the son’s education may be seen as giving access to certain entry-level jobs, which in turn provide opportunities for further career mobility, leading to jobs with varying levels of prestige. In a dynamic model, the timing and sequence of job shifts are of concern, not just the son’s initial condition (i.e., his father’s social status and his own education). In summary, dynamic models are used to explain not only why the later condition of a phenomenon differs from its earlier condition but also how a sequence of changes leads from one condition to the other.

TYPES OF DYNAMIC MODELS

Different types of dynamic models are distinguished on the basis of a variety of formal properties. One basic distinction seems to be whether the components of the system are social actors or the attributes of a social entity. In the former case, dynamic models of the behavior of social actors are developed: Actor A does X, in response actor B

does Y, then actor A does Z, and so on. Although much of game theory is not concerned with dynamic models, some of it formulates precisely these kinds of models. In the latter kind of dynamic model, values of variables describing the social entity are related to one another. Ecological theories of organizational survival utilize these models, for example, relating the degree of environmental variability and the degree of specialization of various types of social organizations in the environment to the survival of these types (Hannan and Freeman 1987). The distinction between systems of actors and systems of variables is not as important as it may seem at first because the behaviors of actors usually can be translated into variables.

A more basic and important distinction is whether time is discrete or continuous. Most empirical phenomena can change at any moment, and this leads one to expect that time should be treated as continuous in most dynamic models. In fact, time more often is treated as discrete for two main reasons. First, the empirical data used to test a dynamic model usually measure time at only a few discrete points. Some researchers then find it convenient to build a dynamic model of the data rather than model the underlying social process. Second, some researchers consider discrete-time models to be simpler and believe that little information is lost from approximating truly continu- ous-time processes with discrete-time models. If the discrete time points in the data are sufficiently numerous and close together, the approximation is almost always satisfactory. If they are not, important intermediary steps in the process are likely to be ignored, possibly resulting in misleading conclusions. Whether discrete-time models are simpler than continuous-time models is less clear. To some extent, it is a matter of a researcher’s taste and training.

Another key distinction concerns whether the variables that describe the social system are discrete, metric, or a mixture of the two. Discrete variables have a finite set of values; for example, political regimes may be categorized into a small number of basic types. Metric variables have a continuum of values; for example, a person’s income and occupational prestige usually are treated as continuous variables. In fact, in both instances, the number of values is finite but is so large that treating the values as continuous may be conve-

nient and is often fairly realistic. Age is a continuous variable, but measurements of it are always discrete (e.g., to the nearest year, month, or day).

A distinction also may be made in the way in which variables in a system change over time. By their nature, discrete variables can change only in jumps. For example, there may be a sudden change from a military political regime to a multiparty government. Metric variables often are regarded as changing gradually. For example, a firm’s profits may be treated as shifting upward or downward by small increments. In fact, metric variables also may change in jumps. For example, income may fall from a high value to nearly zero when a family’s main breadwinners lose their jobs.

Another important distinction is whether the change process is treated as deterministic or stochastic (having a random component). There is a broad consensus that stochastic models are almost always more realistic. Few social changes occur in a strictly determined fashion, and those which do change deterministically are rarely sociologically interesting. Nevertheless, deterministic models can be useful when the solution of realistic stochastic models presents severe technical problems. Those formidable problems tend to occur when there is a high degree of interdependence in the social system (e.g., in models of the diffusion of an innovation) and when both time and outcomes are treated as continuous.

Whether time is treated as discrete or continuous, models of changes in discrete variables are invariably stochastic because changes by jumps almost dictate reference to probabilities. By contrast, continuous-time models of changes in metric variables are typically deterministic.

Some progress has been made in developing empirically estimable stochastic models of heterogeneity in the spread of a social practice in the presence of interdependent influences in a social system (Strang and Tuma 1993). Davis and Greve (1997) provide an intriguing application of this modeling approach to the use of ‘‘poison pills’’ and ‘‘golden parachutes’’ among firms.

Formal dynamic models are of two main types. In one type, the model consists of a set of mathematical equations that relate some elements of the system to other elements. In the other type, the model consists of a set of computer instructions

that relate inputs of various variables and/or actors at one time to outputs at a later time. The computer instructions in fact represent mathematical equations that are so complex that they cannot be solved in practice without the aid of a computer. Still, it is convenient to think of computer models as very complicated mathematical models.

A clear introduction to both discrete-time and continuous-time deterministic models of metric variables can be found in Baumol’s Economic Dynamics (1951), which also introduces several economic theories of potential interest to sociologists, including theories of wages and profits in firms and economic growth. For a discussion of deterministic models of change in metric variables, see Doreian and Hummon (1976).

Two of the early classic discussions of stochastic models of change in discrete variables are Coleman’s Introduction to Mathematical Sociology

(1964) and Bartholomew’s Stochastic Models for Social Processes (1973). Tuma and Hannan’s Social Dynamics: Models and Methods (1984) discusses both deterministic and stochastic models of change in metric variables in continuous time as well as continuous-time stochastic models of change in discrete variables. This work also discusses metatheoretical and methodological reasons for studying social dynamics, applies dynamic models to a variety of different sociological problems, and provides an extensive bibliography pertaining to models and methods used in studying social dynamics. It also contains a comprehensive introduction to event history analysis.

CONCLUSION

Sociologists, whether studying whole societies or small groups, have had a long-standing and farreaching interest in social change. Traditional approaches focused on specific substantive phenomena and, especially in macro-level studies, often stressed unique historical occurrences rather than common dimensions underlying patterns of change. Recent studies of social dynamics usually focus on what is regular and predictable about social change and the social mechanisms that generate a sequence of contingent changes. Often they embed ideas about change in dynamic models and test them in dynamic analyses of over-time data. This

approach has been especially valuable in fostering cumulative research.

(SEE ALSO: Cohort Perspectives; Diffusion Theories; Game Theory and Strategic Interaction; Life Course; Life Histories and Narrative; Longitudinal Research; Paradigms and Models; Social Change; Social Forecasting)

REFERENCES

Bales, Robert F. 1950 Interaction Process Analysis: A Method for the Study of Small Groups. Cambridge, Mass.: Addi- son-Wesley.

Bartholomew, David J. 1973 Stochastic Models for Social Processes. New York: Wiley.

Baumol, William J. 1951 Economic Dynamics: An Introduction. New York: Macmillan.

Bertaux, Daniel, and Paul Thompson eds. 1997 Pathways to Social Class: A Qualitative Approach to Social Mobility. Oxford, UK: Clarendon Press.

Boli, John, and George M. Thomas 1997 ‘‘World Culture in the World Polity: A Century of International Non-Governmental Organization.’’ American Sociological Review 62:171–190.

Carroll, Glen R., and Michael T. Hannan 2000 The Demography of Corporations and Industries. Princeton, N.J.: Princeton University Press.

Coleman, James S. 1964 Introduction to Mathematical Sociology. New York: Free Press.

Davis, Gerald F., and Henrich R. Greve 1997 ‘‘Corporate Elite Networks and Governance Changes in the 1980s.’’ American Journal of Sociology 103:1–37.

Doreian, Patrick, and Norman P. Hummon 1976 Modeling Social Processes. Amsterdam: Elsevier.

Elder, Glen H. 1974 Children of the Great Depression: Social Change in Life Experience. Chicago: University of Chicago Press.

Forrester, Jay W. 1971 World Dynamics. Cambridge,

Mass.: Wright-Allen.

Frank, David J., Ann Hironaka, John W. Meyer, Evan Schofer, and Nancy Brandon Tuma 1997 ‘‘The Structuring of a World Environmental Regime, 1870– 1990.’’ International Organization 51:623–651.

Hannan, Michael T., and Glenn R. Carroll 1992 Dynamics of Organizational Populations. New York: Oxford University Press.

———, and John Freeman 1989 Organizational Ecology. Cambridge, Mass.: Harvard University Press.

Hareven, Tamara 1982 Family Time and Industrial Time: The Relationship between the Family and Work in a New

England Industrial Community. Cambridge, UK: Cambridge University Press.

Pareto, Vilfredo 1935 The Mind and Society, vol. III, Arthur Livingston, ed.; Andrew Bongiorno and Arthur Livingston, trans. New York: Harcourt, Brace.

Ramirez, Francisco O., Yasemin Soysal, and Suzanne Shanahan 1997 ‘‘The Changing Logic of Political Citizenship: Cross-National Acquisition of Women’s Suffrage Rights, 1890 to 1990.’’ American Sociological Review 62(5):735–745.

Sassen, Saskia 1988 The Mobility of Labor and Capital: A Study in International Investment and Labor Flow. Cambridge, UK: Cambridge University Press.

Shubik, Martin 1982 Game Theory in the Social Sciences: Concepts and Solutions. Cambridge, Mass.: MIT Press.

Skocpol, Theda 1979 States and Social Revolutions in France, Russia, and China. Cambridge, UK: Cambridge University Press.

Sorokin, Pitirim A. (1937–1941) 1957 Social and Cultural Dynamics: A Study of Change in Major Systems of Art, Truth, Ethics, Law and Social Relationships, revised and abridged version. Boston: Porter Sargent.

Strang, David G., and Nancy Brandon Tuma 1993 Spatial and Temporal Heterogeneity in Diffusion.’’ American Journal of Sociology 99:614–639.

Tuma, Nancy Brandon, and Michael T. Hannan 1984

Social Dynamics: Models and Methods. Orlando, Fla.: Academic Press.

———, ———, and Lyle P. Groeneveld 1979 ‘‘Dynamic Analysis of Event Histories.’’ American Journal of Sociology 84:820–854.

White, Harrison C. 1970 Chains of Opportunity: Systems Models of Mobility in Organizations. Cambridge, Mass.: Harvard University Press.

Zhou, Xueguang, Nancy Brandon Tuma, and Phyllis Moen 1996 ‘‘Stratification Dynamics under State Socialism: The Case of Urban China, 1949–1993.’’

Social Forces 74:759–796.

——— 1997 ‘‘Institutional Change and Job Shift Patterns in Urban China, 1949–1994.’’ American Sociological Review 62 339–365.

NANCY BRANDON TUMA

SOCIAL EXCHANGE THEORY

Social exchange theory is a major theoretical perspective in sociology. Within this framework, social behavior is viewed primarily in terms of the pursuit of rewards and the avoidance of punish-

ment and other forms of cost. Individuals engage in interaction to meet their needs. The basic unit of analysis is the relationship between actors. Thus, exchange theorists view social relations and the social structures generated by the ties that bind people in different forms of association as the central object of sociological inquiry. Major topics of study within this tradition of research include the nature and effects of the interconnections among actors and the distribution of power within exchange structures. Power and status relations among actors in different types of social structures are considered key forces in determining the nature of structural change over time. The major exchange theorists all have treated power, structural sources of power, and the dynamics of power use as primary in their theoretical formulations.

Social exchange theory derives from several distinct lines of theoretical work in the social sciences, including social behaviorism, utilitarianism, and functionalism (Turner 1986). Major proponents of the social exchange perspective within sociology include Homans (1961, 1974), Blau (1964, 1987), and Emerson (1962, 1972a, 1972b). Within psychology, the work of Thibaut and Kelley (1959; Kelley and Thibaut 1978) bears a strong resemblance to social exchange theory in its emphasis on the interdependence of actors and the social implications of different forms of interdependence. Anthropologists such as Malinowski (1922), Mauss (1925), Schneider (1974), and Levi-Strauss (1949, 1969) have contributed in different ways to the emergence of this theoretical perspective (see Ekeh 1974). In addition, the foundation of microeconomics has much in common with some variants of social exchange theory (Heath 1976). This affinity is clearest in Blau’s Exchange and Power in Social Life (1964) and in subsequent theoretical developments (e.g., Cook and Emerson 1978; Coleman 1972, 1990). The breadth of the intellectual heritage of social exchange theory accounts in part for its continued significance in the social sciences.

Homans’s well-known essay ‘‘Social Behavior as Exchange’’ (1958) clarified the nature of this theoretical orientation and introduced it into mainstream sociology. An elaboration of Homans’s perspective was published in Social Behavior: Its Elementary Forms (revised in 1974). An important distinguishing feature of Homans’s work was its reliance on the language and propositions of behavioral psychology. The use of operant psychol-

ogy as the behavioral basis of exchange theory created much of the early controversy surrounding the utility of this perspective for sociologists. In particular, the corresponding claim made by Homans that laws of social behavior could be ‘‘reduced to’’ the basic underlying principles of psychological behaviorism generated much debate (e.g., Deutsch 1964). According to Homans, ‘‘The general propositions we shall use in explanation are psychological in two senses: they refer to the actions of individuals and they have . . . been formulated and tested by psychologists’’ (1974, p. 12). However, Homans explicitly took as the major theoretical task the explanation of social phenomena. This emphasis on social behavior and the social structures generated and altered by human social interaction has sustained the influence of social exchange theory in sociology. In this regard, Homans viewed the line drawn between psychology and sociology as fundamentally arbitrary.

The initial theoretical formulation developed by Homans (1961) and revised in 1974 included five main propositions, all of which have to do with the fact that behavior is a function of its payoffs: the consequent rewards and punishments. The first proposition is the ‘‘success proposition,’’ which states that the more frequently an activity is rewarded, the greater is the likelihood of its performance. Behavior that generates positive consequences for the individual is likely to be repeated. The second proposition, the ‘‘stimulus proposition,’’ stipulates that similar environmental or situational circumstances will stimulate behavior that has been rewarded on similar occasions in the past. This allows for the generalization of behavioral responses to ‘‘new’’ situations. The ‘‘value proposition’’ specifies that the more valuable the result of an action is to the actor, the more likely that action is to be performed. This proposition is qualified by the ‘‘deprivation-satiation’’ proposition, which introduces the general ideal of diminishing marginal utility. According to this proposition, the more often a person has recently received a particular reward for an action, the less valuable is an additional unit of that reward. Thus, some rewards become less effective over time in eliciting specific actions, though this is less true for generalized rewards such as money and affection and for anything for which satiation is less likely to occur except at extreme levels. The fifth theoretical proposition in Homans’s basic framework specifies the

conditions under which persons react emotionally to different reward situations. This proposition has two parts. People who do not receive what they anticipate are expected to become angry and behave aggressively, based on the original Miller and Dollard (1941) ‘‘frustration-aggression’’ hypothesis (see Homans 1974, p. 37). People who receive more than they expect or do not receive anticipated punishments will be happy and will behave approvingly. This system of propositions forms the original core set of ideas of what has come to be called social exchange theory.

Homans’s (1961, 1974) uses this set of theoretical ideas to explain phenomena such as the exercise of power and authority, cooperation, conformity and competition, structures of sentiment and interaction, status and influence, satisfaction and productivity, leadership, distributive justice, and the emergence of stratification. He addressed these social phenomena primarily in terms of the nature of the interpersonal relations involved. Furthermore, he emphasized ‘‘elementary’’ forms of behavior, or what he referred to as the ‘‘subinstitutional’’ level of analysis. ‘‘We gain our fullest understanding of the elementary features of social behavior by observing the interactions between members of small, informal groups,’’ Homans (1974, p. 356) argued. By studying such forms of behavior, he hoped to illuminate the elementary, informal subinstitutional bases of more complex forms of social behavior that often are more formal and institutionalized. What he bequeathed to modern-day sociology, besides his particular form of theorizing, was an emphasis on the microfoundations of social structures and social change.

Whereas Homans focused on elementary forms of behavior and the subinstitutional level of analysis, Blau (1964, 1987) moved beyond the micro level to the institutional level, dealing with authority and power, conflict, and change in the context of institutionalized systems of exchange. In disagreement with Homans’s reductionistic strategy, Blau (1987, p. ix) claims that his ‘‘theory is rooted in the peculiarly social nature of exchange, which implies that it cannot be reduced to or derived from psychological principles that govern the motives of individuals, as Homans aims to do.’’ In distinct contrast to Homans’s reductionism, Blau assumed that social structures has ‘‘emergent’’ properties that cannot be explained by character-

istics or processes that involve only the subunits. Thus, Blau parted company from Homans in two major ways. First, Blau’s framework was not based on principles of behavioral psychology; instead, he introduced microeconomic reasoning into the analysis of distinctly social exchange. Second, he explicitly introduced the notion of emergent processes into his theoretical treatise, not only rejecting reductionism but also expanding the theory to extend far beyond its original subinstitutional base.

Blau (1964) developed a general framework for analyzing macro structures and processes based on an extension of his micro-level theory of social exchange processes. Drawing on Simmel’s understanding of social life, he explains the general structure of social associations rooted in psychological processes, such as attraction, approval, reciprocation, and rational conduct. Group formation, cohesion, and social integration as well as processes of opposition, conflict, and dissolution are explained in terms of social exchange processes. These forms of social association generated by exchange processes come to constitute very complex social structures (and substructures) over time. These more complex social structures are then examined by Blau as they are created and changed by power processes and the dynamics of legitimation and political opposition. Common values mediate and make possible indirect exchanges and thus the coordination of action in large collectivities. According to Blau, they also ‘‘legitimate the social order.’’ Throughout this major work, Blau contrasts and compares social exchange processes in simple structures with those in more complex social structures and institutions. The major social forces he analyzes include differentiation, integration, organization, and opposition that sets up the dialectic necessary for the explanation of structural change.

The strategy of building a theory of macro structure and processes on an explicitly microlevel theory was a distinguishing feature of Blau’s (1964) original work, which also became the focus of a major stream of theoretical work in sociology on the ‘‘micro–macro link’’ in the 1980s and 1990s. Ironically, Blau (1986) himself challenged the utility of his approach in his subsequent writings (Blau 1987), fueling the debate further. In his introduction to the second printing of his book on exchange and power (1986), he argues that microsociological and macrosociological theories

‘‘require different approaches and conceptual schemes though their distinct perspectives enrich each other’’ (1986, p. xv). This theoretical debate will not be over soon since it lies at the heart of the nature of sociological analysis and relates to broad issues of the primacy of particular units and levels of analysis as well as to complex metatheoretical and methodological issues.

Blau (1964) and subsequently Emerson (1962, 1972, 1972b) made power the central focus of analysis. Blau treated power, authority, opposition, and legitimation as key topics in his discussion of macro structures and the dynamics of structural change. Emerson’s (1962) theory of pow- er-dependence relations was partially encorporated into Blau’s (1964) treatment of power imbalance and the conditions of social independence. For Emerson (1962), these strategies were power-bal- ancing mechanisms. The central proposition in Emerson’s (1962) article classic was that power, defined in relational terms, is a function of the dependence of one actor on another. In a twoparty exchange relation, the power of one party

(A) over another party (B) is a function of the dependence of B on A. Dependence is a function of the value one actor places on the resources (or valued behavior) mediated by the other actor and the availability of those resources from alternative sources. The greater the availability of these resources from other actors (or alternative sources), the lower one actor’s dependence on another. Two features of this approach to power are important: (1) It treats power as relational (a feature of a social relation, not simply a property of an actor), and (2) it treats power as potential power; that is, it may or may not be exercised. This relational conception of power became the basis for most subsequent work on exchange and power.

Emerson (1972a, 1972b) expanded his treatment of power and dependence to form a more extensive exchange theory of social relations. In many ways, his work combined the approaches of Homans (1961) and Blau (1964). In the original formulation, Emerson (1972a) adopted the language and principles of behavioral psychology to form a theory of social relations. However, he quickly moved beyond behavioral principles to the formation of more complex propositions regarding the emergence of various kinds of social structures. Here the theory picks up the Simmelian focus of Blau’s work as well as the concern with

emergent properties and complex social structures. Emerson (1972b), like Blau (1964, 1986), viewed the major task of exchange theory as the creation of a framework in which the primary dependent variable is social structure and structural change. The major task was eminently sociological, not psychological, even though all three theorists explicitly encorporated into their thinking notions about the psychology of actors. Emerson and Cook’s subsequent work (e.g., Cook and Emerson 1978) adopted a more cognitive perspective on the actors involved in social exchange. Molm’s (1981, 1987) earlier work extended the original behavioral underpinnings of the theory.

Exchange theory, though originally dyadic in focus, has been extended to apply to the analysis of exchange networks. Both Homans and Blau recognized the ubiquity of social networks and different forms of social association, but Emerson (1972b) made networks and corporate groups a central focus of his theoretical formulation. The definition of exchange relations as being ‘‘connected’’ in various ways to form network structures was the key to this development in the theory. Emerson defined two major types of connections between exchange relations: negative connections and positive connections. Two relations are negatively connected if the magnitude or frequency of exchange in one is negatively correlated with the magnitude or frequency of exchange in the other. In essence, the two relations are strictly alternatives. If a supplier gets parts in an exchange with one vendor, he or she does not need to get the same parts from another vendor. Negatively connected relations are thus competitive in nature. In contrast, when two relations are positively connected, exchange in one relation enhances exchange in the other. For example, the resources one party gets in exchange with one supplier can be used to obtain needed goods from another supplier. In this case, a positive connection exists and the two exchange relations are positively correlated. Such exchange relations are more cooperative than competitive in nature and form the basis for some types of division of labor and specialization within exchange networks. Subsequent theorists such as Willer (1987), Markovsky et al. (1988), Bonacich (1986), and Yamaguchi (1996) have developed other ways of classifying types of exchange connections. Some of this work is discussed below in the discussion of alternative perspectives.

A key concept in Emerson’s exchange theory of power is the idea that exchange relations can be balanced or imbalanced. A power inequality results from an imbalance in power relations between two or more actors. An exchange relation is balanced if both parties are equally dependent on each other for exchange (or resources of value). If they are equally dependent, they have equal power. The central idea that power is based on dependence allows for the specification of ways in which dependencies are altered so that they affect the balance of power in the exchange relation and in networks of exchange relations.

Emerson postulated four power-balancing mechanisms to explain some of the ways in which exchange relations and the networks they form change either to maintain and preserve existing structural arrangements and distributions of power or to alter them. Coalition formation is one of the mechanisms by which power-disadvantaged actors in less powerful network positions can gain power through the collective advantage gained through cooperative action. Not all coalitions are powerbalancing, however. In subsequent work, Emerson addressed the kinds of coalitions that form between powerful actors (sometimes referred to as collusion) or between powerful actors and a subset of the less powerful actors (a divide-and-conquer strategy).

Division of labor, or specialization within a network, may operate as a power-balancing mechanism, since it can result in changes in the distribution of power in a network through modifications in the distribution of resources and the nature of the structural arrangements. For example, two suppliers of the same resource who have been competitors may decide to specialize and offer different services in a way that makes them no longer competitive with each other in a particular network. Network extension also can alter the balance of power in a network as new exchange partners become available. In addition, when other strategies are not available, actors can devalue what they obtain from a more powerful actor as a way to reduce their dependence on the relationship. This strategy may be a precursor to an exit from the relation in many instances. Various theorists have continued this line of work, specifying the principles that predict the distribution of power in different exchange structures and the

processes that modify it (e.g., Cook et al. 1983, 1986; Bonacich 1986; Yamaguchi 1996).

Other extensions of the exchange theory originally developed by Emerson have focused on the links between structure and process and on other bases of power. In a major research program that extended over a ten-year period, Molm (1997) investigated the role of coercive power in social exchange. Emerson’s work and that of most of the exchange theorists had focused almost exclusively on reward power, or the control over positively valued goods and services. Coercive power is the ability to control negative events (e.g., to withhold rewards) or to inflict punishment on another in an exchange relation. Unlike reward power, coercive power is used less often in exchange relations, especially by those in power-advantaged positions, who seem to understand that it may be viewed as unjustified in many circumstances. The fear of retaliation is also a deterrent to the use of coercive power. The use of coercive power is more costly since it imposes losses on the exchange partner in addition to the opportunity costs involved. Molm’s (1989, 1997) major accomplishment was to expand the treatment of power in the classic powerdependence formulation to include forms of coercion. Since exchange relations often involve control over both things people value and things people wish to avoid, this is a significant extension of the theory.

Alternative theoretical formulations have been developed for investigating power processes in exchange networks. They include the ‘‘elementary theory’’ developed by Willer and his collaborators (e.g., Willer and Anderson 1981; Markovsky et al. 1988), Friedkin’s (1992) ‘‘expected value model’’ of social exchange, and game theory, which has been applied to the analysis of exchange networks by Bienenstock and Bonacich (1992). While some of these formulations have an affinity with the original power-dependence framework developed by Emerson (1972a, 1972b), most have explored other bases of power. For example, Willer and his collaborators have developed a different terminology for specifying the nature of the relations in an exchange network. They define three types of relations: null (no connection), inclusion (when someone has to be involved in an exchange for it to take place) and exclusion (when someone may be involved in an exchange but is in competition with others and thus may be excluded from the

exchange at any time). These theorists go on to develop different principles for the distribution of power in networks characterized by different types of relations. Exclusion is viewed as the main determinant of power. The ability to exclude others from exchange is thus the key source of power in this theory.

Bienenstock and Bonacich (1992, 1997) analyze exchange networks by using a game theory perspective. They attempt to understand the efforts of actors to maximize certain well-defined interests by adopting strategies that can be analyzed usefully with the tools of game theory. Based on different solution concepts (e.g., the core, the kernel), they make predictions concerning the outcomes of the exchanges in various types of network structures. In addition, this application of game theory provides predictions about the role of information in exchange processes. Building on the early contributions of Blau, Coleman, Emerson, and Cook, Yamaguchi (1996) works out a rational choice model for predicting the distribution of power and the effects of network centrality in what he terms substitutable and complementary exchange relations.

Further developments in the theory of exchange include the formulation of explicit propositions concerning the use of power in different types of exchange network structures and the specification of some of the determinants of power use. These factors include concern over the fairness of the distribution of outcomes, the commitments that emerge between actors (e.g., Lawler and Yoon 1996), the formation of coalitions, particular strategies of action, and whether the power is reward power or punishment power. More recent developments focus more on methodologies for specifying the distribution of power in complex network structures (see, for example, Markovsky’s work). Interest in this topic is in part driven by the potential for synthesizing exchange theoretic conceptions of power with network models of social structure (see Cook 1987; Cook and Whitmeyer 1992). Another arena of current theoretical and empirical work is the specification of dynamic models of power use and structural change that include a more sophisticated model of the actors involved and the strategies they adopt in their attempts to obtain resources and services that are of value to them. These general theoreti-

cal and empirical efforts will be important if exchange theory is to fulfill its promise of providing an approach to linking micro-level theories of action and interaction with macro-level explanations of structure and processes of social change, an agenda that was originally set by Homans, Blau, and Emerson.

The application of exchange theory to understanding a variety of social phenomena has grown over the last two decades. Early applications focused on the explanation of the initiation and termination of social relations in work settings and families and then in the domain of romantic relationships and dating. Topics of interest to researchers included the conception of fairness in social exchange relations and its link to relational satisfaction and dissolution, the use of power in social relations based on control of both rewards and costs, and the abuse of power as well as the role of coalitions in altering the balance of power among actors in a network of individuals or organizations. Beyond the application to family and work settings, exchange theory has been applied in many different contexts to the study of organizations and interorganizational relations. Since organizations typically require resources from other entities much of their time is devoted to the strategic management of those dependencies. The resource dependence perspective (Pfeffer and Salancik 1978) in the field of organizations represents a straightforward application of exchange reasoning to the strategic actions of organizations and their subunits (e.g., at the divisional level). The developing field of economic sociology is now drawing to some extent on ideas derived from exchange theory to explain the emergence of network forms of organization and the nature of the power processes that emerge in those networks. Network effects on labor practices, informal influence among organizations, the organization of business groups, and the formation of international linkages that cross traditional national boundaries of economic and productive activity are central topics of inquiry in economic sociology. Some of these efforts involve understanding the effects of network location on outcomes and the various strategies actors use to enhance their bargaining power and influence. These efforts derive in part from the power-dependence reasoning first introduced by Emerson and Blau into exchange theorizing.