Diffusion Theories Versus Economic Theories

The debate on the roles and relative importance of diffusion and structural change in fertility transition has been one of the most active debates in the demographic literature on diffusion, and the workshop discussion reflected it. Few people would argue that either cause operates entirely by itself; the issue is how much emphasis should be placed on each.

Structural changes that could affect fertility could include both economic changes, such as changes in labor markets and increases in the costs of schooling, and noneconomic changes, such as increases in child survival. During the workshop, Cleland gave little weight to economic changes alone. Having defined the blended and pure versions of diffusion theory discussed earlier, he suggested that the pure version is not a plausible explanation for fertility decline in the developing world. He proposes that diffusion of birth control in these countries has followed declines in infant and child mortality and is not a response to structural economic change: "Fertility decline in the developing countries is essentially a lagged response to improved survival. ... I see little explanatory space for transformations in the economic value of children." In contrast, for the European transition, the spread of marital fertility control does not appear to have been linked to mortality decline. Thus, according to Cleland, "The pure version of the innovation-diffusion explanation remains compelling for this region of the world."

Cleland's views were not widely shared. Lesthaeghe, for example, responded by stating that a correct reading of the results of the Princeton European Fertility Project would not give exclusive credit to cultural forces. To illustrate, he cited Knodel's (1974) analysis for Germany, which emphasizes structural and economic change. Lesthaeghe voiced the view of a number of the workshop participants when he stated emphatically that the explanatory power lies not in culture versus economics, but in culture and economics. In the European work, he explained that adding cultural variables to the model increased the model's explanatory power.

Indeed, the issue of whether the two phenomena can be separated was addressed by several of the workshop participants. While Palloni had earlier highlighted how many researchers distinguish between these two competing theories of fertility transition, he now argued that in fact they cannot be considered to be separate—a point that has obvious implications for whether it is possible to disentangle the effects of the phenomena in order to study them (Palloni, 1998:3):

Analytically useful diffusion models require theorizing about social structures, about the positions that individuals occupy in them, about individual decision-making processes that accompany adoption of a behavior, and about the constraints these individuals face. I conclude that it is unilluminating to confront diffusion theories with competing explanations that regard behaviors as responsive to "structural" factors, such as socioeconomic positions or social class membership, as if diffusion processes did not require or could proceed independently of structural factors that characterize the environment where individuals act and where behaviors take place.

Researchers who pit diffusion against structural change are making a spurious distinction, he continued, since both have their basis in rational decision-making on the part of individuals (Palloni, 1998:9):

Diffusion only occurs because individuals decide to adopt after observing others do so, and after updating their information by including observed outcomes associated with others' adoption into their own decision making process. ... A diffusion model rests on assumptions and imageries not dissimilar to the ones that prevail when, for example, we refer to individuals changing their fertility behavior as a result of socioeconomic changes that affect them (the so-called demand theories of fertility). The vast majority of applications of diffusion models in both demography and sociology neglect this very simple tenet of diffusion models: adopters and non-adopters are rational decision-makers and adoption is the outcome of a rational decision-making process.

Carter took a similar position. Yet while Palloni argues that social interaction must be understood in the context of rational decision making, Carter (1998:31) posits that individual rational choice must be placed in the context of social learning:

In the population studies literature, social learning is held to be conceptually distinct from individual rational choice even though the results may be empirically indistinguishable. But if learning is always social, it is not clear what space is left for economic accounts. How would actors make economic choices if they did not know of the existence of behavioral options and if they were ignorant of their risks and normative evaluations? How would they learn of these things except through interaction with others? What would nonsocial learning consist of? When we observe social learning are we not also observing the socially distributed character of economic decision-making?

Similarly, Kertzer suggested that economic systems may best be viewed as cultural constructs. Thus, economic change is also cultural change.

Durlauf described the parallels between the view that diffusion and structural change are inseparable and the emergent economic theory of social interaction. In the latter theory, "the role of individual incentives emphasized by economists is integrated with the social norms and networks stressed by sociologists." The implication for the issue at hand is that "the diffusion process is not simply a mechanical 'carrier.' Rather, the behavior or factors giving rise to the social interaction are an integral part of the theory that make it impossible to separate the diffusion process from its source(s)." Durlauf presented a model based on this symbiosis that can be used to analyze the adoption of modern contraception.

Durlauf agreed with Cleland's depiction of a blended diffusion theory, in which structural transformation is the main mechanism of fertility change and diffusion merely facilitates the process. Although he emphasized the critical role of social interactions, he concluded that those interactions alone are not sufficient. He posited that "economic conditions drive the process, [and] are then amplified by social interactions." Yet he emphasized what he referred to as "the insight of the social multiplier": economic conditions need only change enough to get a few early adopters to switch behavior. Then once in play, endogenous exchanges among agents (i.e., social interactions) ultimately drive the fertility transition.

Palloni introduced the idea that "as the process of adoption of [an] innovation progresses, the social and economic environment are modified by the process of adoption itself." He noted that diffusion transforms the social structure in which it occurs, and this transformation feeds back into the diffusion process. For example, early adopters of fertility control can provide more education for their children, thus acquiring more power and prestige. This in turn may lower the costs for others of adopting birth control. Carley made a similar point, noting that diffusion alters both the underlying cognitive and social structures of those involved. Such endogenous feedback further complicates analysis of the underlying process of change.

Lesthaeghe offered a mathematical formulation of the interaction between diffusion and structural change, adapted from the three well-known preconditions for the adoption of a new mode of behavior: being ready, willing, and able (Coale, 1973). Lesthaeghe explained that success with respect to the adoption of a new form of behavior is dependent on meeting the three preconditions jointly, "and that the outcome will be determined by the weakest link among the three." Thus, he regards the "'economics versus culture' formulation as a dead-end street" (see also Lesthaeghe, 1997).

Lesthaeghe presented a conceptual model for the interaction among the three preconditions; applied this model to Montgomery and Casterline's (1996) formulation of the impact of social factors; and used the model along with data from the Demographic and Health Surveys (DHS) to categorize African women on a scale from ready, willing, and able (RWA) to none of these, and to identify bottlenecks to adoption based on the planning status of the next pregnancy. The results of the exercise indicate that "factors associated with low readiness and ability tend to be responsible for the bottlenecks at the onset but that the willingness condition is likely to become the weakest link at a later stage." The results also suggest that the nature of nonwillingness shifts over time from being associated with ethical, religious, or social objections to being based on health-related fears. There are clear policy and program implications of these findings (see last section of this report). Throughout, Lesthaeghe stressed that a failure to consider all three preconditions and their interactions will lead to an incomplete understanding of the fertility transition in a given setting.

Sinding observed that it is difficult to separate diffusion by a family planning program from the causal impact of structural economic changes if among the notions diffused by the program is the idea that there are economic benefits to small families.

Importance of Cultural Context

Lesthaeghe also emphasized the importance of context or culture in determining the relative roles of Coale's ready, willing, and able components: "The correlations between R, W, and A can vary substantially across contexts (e.g., countries, neighborhoods, social groups), and the assumption of complete endogeneity of W is not likely to hold. For instance, counterpropagation or gossip about the physical effects or comfort of contraception can reduce willingness considerably, even if R and A would be high." Determining the mix of ready, willing and able in a particular setting and identifying the contextual or cultural factors that influence this mix is essential if family planning policies and programs are to deliver appropriate messages to encourage the adoption of birth control.

The essential role of context or culture in fertility transitions was emphasized by several other participants. As noted above, Cleland stated that fertility decline in the developing world should be viewed basically as a lagged response to declines in infant and child mortality. He suggested that "the length of the lag probably depends on cultural and political factors that condition the ease with which, and the speed with which, the new reproductive regime is incorporated." Durlauf suggested that variations in context "characterized by the level and relative importance of economic and cultural factors" account for differences in the level of economic development that will initiate a fertility transition. "Some cultures," he noted, "may possess strong proscriptions against fertility control or the economic benefit of children may be so large [as] to mandate high levels of economic development to induce even a few individuals to change their behavior." Kertzer agreed and cited Cleland's failure to address class and gender differences, suggesting that "economic, demographic, and political factors all play a role—but all within the cultural context.''

Similarly, Palloni emphasized that "diffusion processes are affected by the social structure of the systems within which they are occurring." In particular, sociocultural factors are an important determinant of the rate of diffusion in a given setting, and, as also suggested by Lesthaeghe, can as easily hinder as facilitate adoption: "the observed regional clustering of fertility changes in Western Europe could be explained by social or economic factors that halted or slowed down a diffusion process already on its way in other regions."

Sinding offered a counterpoint to the emphasis on cultural differences. He observed that increasing globalization and the spread of mass communications act to counterbalance the importance of such differences—for example, by spreading ideas about the benefits of small families and fostering the desire for more consumer goods.