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National Research Council (US) Committee on Population; Reed H, Briere R, Casterline J, editors. The Role of Diffusion Processes in Fertility Change in Developing Countries: Report Of A Workshop. Washington (DC): National Academies Press (US); 1999.
The Role of Diffusion Processes in Fertility Change in Developing Countries: Report Of A Workshop.
Show detailsThe channels through which diffusion may occur fall into two broad categories: social networks and mass communications. Although this distinction can be blurry, it can still be conceptually useful, and the workshop presentations tended to divide along these lines. In addition, within each of these broad categories, various specific channels can be identified. Social networks exist at the personal level, at regional and national levels, and, increasingly, at the international level, and they may involve direct or indirect contact. For mass communications, the channels include television, radio, and the Internet, as well as print media. The various channels of diffusion are not only interrelated, but also mutually reinforcing.
Social Networks
A number of models have been developed to characterize the social networks through which diffusion may take place. As suggested by Kathleen Carley, individuals acquire and use information within networks composed of multiple sets of actors and connected by a variety of different relationships. The number and complexity of the social networks in which individuals are involved varies with the level of development and the cultural context. The implications of this for the diffusion of fertility control are addressed below.
Several characteristics of social networks were discussed by Marsden, who observed that the decision to adopt a new product, idea, or behavior depends on characteristics of both the individual and the surrounding social structure. Focusing on social structure, he identified two broad types of relationships that may exist between individuals. The first is social cohesion, which can involve either direct contact between actors or indirect ties, whereby influence is transmitted through intermediaries. Direct and indirect ties may also work together. For example, one actor's decision to adopt an innovation may be influenced by direct contact with another and amplified by the indirect influence of other actors that intervene between the two. The second type of relationship identified by Marsden is substitutability or equivalence of positions. Such relationships may also be of two sorts: structurally equivalent actors are substitutable because their relationships to other actors are identical; role equivalent actors are substitutable because they have similar relationships to similar types of actors. Structurally equivalent actors will also be role equivalent, but the reverse is not necessarily true. Neither structurally equivalent nor role equivalent actors need to have direct contact with one another; thus, the social mechanisms through which diffusion occurs between actors have to be specified.
Marsden noted that social networks can provide access to information about an innovation and influence the adoption of an innovation. Networks create "opportunity structures for contact and information transfer." They also influence the adoption of innovations by providing a mechanism for social comparison (Erickson, 1988). Decisions to adopt innovations are generally made in a context of uncertainty about the best action to take, and individuals tend to look to a reference group to determine the costs and benefits or the normative implications of adoption. The reference group may be one with which the individual has ties of social cohesion—either solidarity ties (e.g., kinship or friendship), which tend to link coequals and thus generate homogeneity, or linkages of authority, which are asymmetric. Or the reference group may consist of peers (who are neither friends nor relatives) who hold similar positions within the social structure. The individual models his or her behavior on that of these structurally similar others, who need not even be aware of their influence (Marsden and Friedkin, 1993). Marsden noted that linking and interaction usually increase with attitudinal and behavioral similarity, so that the diffusion process alters the social networks involved.
Palloni offered a similar taxonomy of social networks, identifying four mechanisms of interpersonal relations that characterize the social context for adoption decisions. The first is relational linkages within a given setting or network. There are two significant aspects of these linkages: the density of individual connections and connections between actors inside and outside the network. The second mechanism is structural linkages, based on similarity of structural position (Burt, 1987). Unlike Marsden, however, Palloni noted that such linkages can result in either imitation or divergence (resistance to adoption), a matter that requires empirical study. The third mechanism is spatial proximity. Finally, fourth is the influence of culturally bounded groups (Strang and Tuma, 1993), defined by relations with others "based on definitions of actions, status, and purpose."
Homogeneity Versus Heterogeneity
The classic view of diffusion, expressed by Cleland, emphasizes the importance of homogeneity for the diffusion of an innovation. The use of contraception spreads rapidly throughout socially and linguistically homogeneous systems, regardless of the position of groups within the economic structure. The commonality of language is a particularly cogent factor associated with the spread of parity-specific fertility control in Western Europe during 1880-1930. Threshold theory, however, holds that there must be an initial level of acceptance before innovations can spread, even through a homogeneous population.
Assuming that an innovation is very likely to spread more rapidly among homogeneous groups, Lesthaeghe argued that the diffusion process begins with a small group of innovators who are capable of influencing the rest of the population. Similarly, Carley observed that "central" individuals—those with more connections to others—are more likely to acquire new information (Freeman, 1979; Weenig and Midden, 1991) and that individuals who are on the periphery of a social structure may be more likely to act on new information and thus generate innovative behavior within the group (Burt, 1973, 1980; Lin and Burt, 1975).
Highly homogeneous groups are not as likely as more heterogeneous groups to receive and be receptive to new ideas and behaviors. Increased levels of economic development open up new channels for diffusion, exposing new members of formerly homogeneous groups to more heterogeneous information and influences. Bongaarts and Watkins (1996) suggest that this process facilitates the diffusion of fertility control. These themes were reiterated by Carley, who, drawing on the evidence from the psychological literature on diffusion, noted that "information flows more quickly in integrated groups ... but only if the groups are relatively small and have relatively simple cultures" (Carley, 1991; Kaufer and Carley, 1994). In addition, Palloni observed, "it is in homogeneous groups where sanctions are more likely to be applied efficiently against individuals who depart from conventional norms. Under these conditions, it would be individuals in heterogeneous social settings that would be more able to change their behavior."
Entwisle described the study she and her colleagues recently conducted in Nang Rong, Thailand, which addressed the question of the relationship between homogeneity and the adoption of a new form of fertility control (injection of hormonal contraceptives). In earlier work based on data from 1984, Entwisle et al. (1996) found that within each village of Nang Rong, one contraceptive method tended to dominate, because of "the conservative influence of local conversation networks on the choices made by individual women in Nang Rong." Between 1984 and 1994, the social world of the villages extended progressively beyond their boundaries as a result of migration, a dramatic increase in the spread of television, and major improvements in the road system. Entwisle and her colleagues tested two hypotheses in their most recent study: (1) distinctiveness in contraceptive method preference between villages decreases as the influence of local networks lessens and linkages to other villages and the national culture increases and (2) village centrality within a network of labor exchange in the district (i.e., the number of direct ties to other villages) is positively associated with increased adoption of the new method of contraception. She reported that the first hypothesis was supported by the data but the second was not. Indeed, it was found that village centrality had a greater association with the use of old methods than with the adoption of a new method. Citing several possible confounding factors, Entwisle noted that further work is planned to explore these unexpected findings.
A final point regarding homogeneity of social networks was made by Carter, who described the challenges to researchers who do empirical work on diffusion. The idea that communities are culturally homogeneous is rejected by some anthropologists. He suggested that "many anthropologists are prone to see rather less community and a great deal more variation in social structure. The dimensions of this variation include systems of kinship and marriage, social stratification, and relationships to state institutions." Kertzer expressed a similar point of view, citing evidence from nineteenth-century Italy that contradicts the idea that once contraception reaches a certain level, it spreads rapidly through a community. In Italy, heterogeneity in social class served as an obstacle to communitywide change.
Spatial and Emotional Proximity
Spatial proximity is generally assumed to facilitate diffusion because people tend to have more interaction with and be more influenced by those who are physically close. Spatial proximity also affects the flow of information between organizations and nations. However, Carley suggested that what matters most is not physical distance per se but perceived distance, so that communication bridges that appear to increase the physical proximity among people are thought to be critical to successful innovation (Allen, 1977). Thus, linkages through modern telecommunications can create a perception of proximity that replaces actual physical closeness.
As indicated in the discussion of homogeneity, the characteristics of those who are in close spatial proximity to one another may sometimes act as a barrier to rather than a facilitator of diffusion. This point was expressed by Palloni, who suggested that various mechanisms can operate to render spatial proximity a means to either promote or discourage adoption of innovations.
There is no consensus on the question of whether "strong" ties (connections to those with whom one has daily contact) or "weak" ties (connections to those whom one sees infrequently) are more important channels for the diffusion of innovative ideas. Indeed, even definitions of strong and weak ties are not standard (Granovetter, 1973). Cleland suggested that both are important, but emphasized the influence of those with whom one interacts daily. Citing the work of Susan Watkins and her colleagues in South Nyanza, Kenya, he noted that "the experiences of close friends, neighbors, and relatives appear to be of particular importance." Carley, in contrast, pointed out that individuals are more likely to seek information that is sensitive, unknown, or threatening from those with whom they have weak (or irregular) ties (Granovetter, 1973). Montgomery suggested that the social identity of other actors in a network—the depth of information they possess, their credibility, and force of example—may determine whether a weak tie is activated. The study in Nang Rong by Entwisle et al. (1996) was specifically designed to explore the influence of weak ties on method diffusion, but the study results were mixed.
With regard to direct (personal) versus indirect (impersonal) ties, the former appear to be more important for diffusion. Goldman described a study conducted to examine the diffusion of beliefs about hygiene—specifically with regard to diarrheal disease—in rural Guatemala. Goldman and her colleagues hypothesized that belief in the link between hygiene and diarrheal disease would be most common among women who knew others outside the community and among those living in communities that had significant contact with the outside world. They also hypothesized that women who were involved with community organizations or who had family members who were involved in these organizations would be more likely to hold such a belief because of their increased contact with innovative ideas circulating in the community. The study results showed that personal contacts exerted a greater influence on beliefs than did impersonal contacts (the latter being represented by exposure to mass media and the presence of a water committee in the community). In particular, having a relative living abroad or in Guatemala City proved to be the most important channel for hygiene-related beliefs; participation in community groups was also significant.
That is not to say, however, that indirect or impersonal ties have no role in diffusion. As suggested by Marsden, indirect ties may operate through intermediaries—exemplified by the "innovators" who are first to adopt a new technology or behavior. Moreover, the influence of ties of structural equivalence may not involve direct contact at all. Citing Weimann (1994), Marsden also noted that opinion leaders and their social networks have a far greater influence on adoption of family planning innovations than they do on creating awareness of these innovations.
Mass Media Effects
It is impossible, of course, to discuss the role of diffusion without addressing the role of mass communications, particularly television. Just 15 years ago, many countries (e.g., China, India) were not broadly exposed to mass media, especially television. Today the situation is quite different. There is evidence in Brazil that, even among poor families, one of the first major purchases that many people make is a television, and the most-watched programs are news and soap operas (Hornik and McAnany, 1998).
Television is often an important source of new information. Carley cited Gantz et al. (1986) in noting that 80 percent of subjects discussing a local news event got their initial information about the event through interpersonal channels, but they received follow-up details predominantly from the mass media. Carley suggested that "the mass media often become the primary source of details on new information because of its one-to-many capabilities and its ability to transmit an encapsulated message with less change in that message." Goldman reported that general programming on radio was not found to be a significant source of information about hygiene norms in Guatemala. However, she suggested that since so many rural women listen to radio or watch television frequently, those media might be used to transmit specific health-related information.
Robert Hornik cited evidence of the very strong association between access to mass media and fertility at several different levels. At the national level, estimating a regression equation for 102 countries shows that television sets per capita accounted for 82 percent of the variance in fertility in 1990 (excluding three oilrich countries that were statistical outliers). In addition, Potter et al. (1998) found a large association between television ownership and fertility at the municipality level in Brazil. Finally, Westoff and Bankole (1997) have demonstrated the association between media access and fertility intentions and behaviors for individuals in seven African countries.
One potential problem with many studies of mass media effects is the possibility of selection bias. At any time, those who are already using contraception or who are considering using contraception are likely to be the most receptive to media messages about contraceptive use. In cross-sectional studies, this will result in an association between contraception and mass media messages that is not due to the latter affecting the former (Westoff and Rodriguez, 1995; Bankole et al., 1996). While acknowledging the need for caution in drawing causal inferences from correlational data, Hornik noted that relationships between television and fertility are as strong as or stronger than those between gross national product (GNP) per capita and fertility, and are still statistically significant when controlling for GNP. Hornik cautioned against automatically concluding that individual exposure to television results in individual fertility reductions. Rather, the evidence indicates aggregate-level effects: nations or municipalities in which television is more widely available are those in which there is lower fertility.
Hornik set forth four hypotheses about the pathways through which the media may influence fertility:
From a policy perspective, it is useful to know whether direct, program-related messages or indirect, more generalized, longer-term messages are more effective in diffusing fertility control. In reviewing the evidence on direct messages, Hornik observed that their effects appear to be limited in two ways. First, they help increase demand for clinics but do not seem to show clear effects on individual-level behavior. Second, their effects last only as long as the media program is ongoing. Thus, direct messages would appear to have short-term effects on those who are ready to act but need a final push. Indirect messages, however, may have their greatest effect on those who are aware of a new behavior, but do not yet intend to adopt it. This influence may occur over a substantial period of time and require repetition and reinforcement through multiple channels (as discussed below). Finally, Hornik suggested a further type of media effect: "the effects of continuing messages delivered through the IEC [information/education/ communication] efforts of general pro-family planning programs ... not in the context of a discrete intervention." Study of the influence of such messages may reveal longer term effects than those observed in short-term evaluations of discrete programs. Of course, it should be noted that IEC campaigns may be viewed by some as propaganda rather than policy.
Many of the workshop participants agreed with Hornik's emphasis on the importance of indirect messages. Joseph Potter, for example, presented evidence from Brazil that indicates that television "reinforced the incorporation of audiences into a national consumer market, attached ideas and values concerning family structure and women's role in society, promoted a strong positive image for consumption, and prompted new ways to think about the relation of sex and reproduction" (see Faria and Silva, 1983; Faria, 1988; Faria and Potter, 1990, 1997). Potter suggested that diffusion through Brazilian television is strengthened by the fact that there is no explicit government policy to promote family planning, as well as by "the highly autonomous, dynamic, and uninhibited nature of Brazilian television programming." According to Potter, Brazilian television programming transmitted messages that promoted consumption and a consumer-oriented life-style that is incompatible with having large numbers of children, as well as the preservation of youth and beauty. Small families were consistently depicted, as were modern gender and intergenerational relations. The accomplishments of modern medicine—relevant to the eventual emphasis in Brazil on surgical sterilization during cesarean section deliveries—were also underscored.
Other Channels
Channels for diffusion include not only ties to individuals or the mass media, but also ties to entities ranging from family planning programs to government to international organizations to the global community (through modern telecommunications such as the Internet). Mason and Sinding argued that the role of population policies and programs on the diffusion of fertility control is often underestimated. They observed that there actually is strong evidence for the effects of population policy on fertility decline, but that such effects are often "accelerative" rather than "originative" and are at times ineffective, especially in the least-developed countries. Mason and Sinding cited specific evidence from "countries in which structural conditions for fertility change have been inauspicious or even antithetical to change, but in which population programs were instituted or strengthened and fertility declined rapidly thereafter." They suggested that the "diffusion" created by family planning services is a diffusion of technical knowledge and information about the location of the nearest services.
There is no clear evidence on whether programs and policies also influence the demand for children by diffusing ideas about the value of children and alternative means of enhancing family socioeconomic status. Sinding suggested that governments have played an important role in fertility decline by sanctioning a form of behavior that represented a revolutionary change in what institutions had been teaching. Duff Gillespie agreed that governments can play an active role in the diffusion of new ideas. He suggested that more emphasis should be placed on the "social engineering" aspects of diffusion of fertility control: he noted the example of how government support in Bangladesh and India helped to diffuse knowledge of the benefits of oral rehydration therapy for infants suffering from diarrhea.
Susan Watkins presented a rich and highly detailed history of the transformation of population ideology in Kenya. The conventional view emphasizes the activities of the Kenyan government, but her account stressed the vital and frequently neglected role that the international population movement played in this transformation. "The global networks disseminated and altered population ideologies" and influenced Kenyan elites. Watkins suggested that Kenyan elites had little inclination to adopt the ideologies of the population movement, but did so for two primary reasons. First, the Ministry of Economic Development and Planning was influenced by neo-Malthusian logic. Second, however, the Kenyan elites "wanted to signal that Kenya was not a backward nation, that it was a member of a global community."
This increasing role of globalization—both economic and cultural—must also be acknowledged. Gillespie emphasized the importance of "global dynamics" or "sea changes," although such influences are difficult to analyze. Bongaarts and Watkins (1996:668) make the following distinction:
National channels of social interaction are particularly relevant in understanding the pace of national fertility transitions once they have begun, whereas global channels are particularly relevant to the timing of the onset of fertility transitions across countries and thus to the pace of global fertility transition. ... Given current levels of economic development and the proliferation of global channels of interaction, we expect that over the next three decades or so few countries will fail to experience the onset of a fertility transition.
Yet another key point to emerge from the discussion of the various channels for diffusion was the mutually reinforcing effects of multiple channels. In discussing various types of linkages between individuals, Marsden suggested that "in the idealized case, direct and indirect influences reinforce one another." In particular, a direct connection can be reinforced by several indirect connections. Montgomery emphasized the dynamic nature of diffusion, especially the multiplier effect through which the information diffused by a program can spread through social networks. This point was also emphasized by Hornik, who noted that through social networks, ''the effects of mass media diffuse beyond those who are directly exposed to the content." Indeed, Hornik suggested that people may change their behavior "when many aspects of their environment communicate new messages in a repeated and reinforcing way over time."
Sinding cited Kenya as an example of the kind of multifaceted diffusion approach that appears to be most effective for policy makers. Diffusion of fertility control in that country involved a formal information/education/communication program, speeches by the president, village meetings, calendars, field workers visiting households, and village women gossiping about family planning. Thus, the effect of any one channel cannot be separated; rather, emphasis should be placed on the way in which various channels can collectively encourage the adoption of ideas, values, and behaviors associated with fertility decline. More research is also needed on the specific messages that are passed from providers to clients and how these messages are interpreted.
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