In our earlier analyses we have focused on fertility change in developing countries. It is therefore essential to ask whether social interactions open similarly new perspectives to the analyses of fertility in developed countries as in developing countries. In the former countries, analysts frequently presuppose the existence of rational fertility decisions and thus argue that increasing individualism has liberated fertility decisions more and more from the fetters of social norms and cultural constraints. In this chapter, however, we argue that even in developed countries an individualistic perspective on fertility is not sufficient. In addition, social interaction is an important aspect in understanding fertility change and fluctuations in birth rates. Social interaction in this chapter is defined as the phenomenon that an individual's behavior depends on macro-level conditions—typically social or cultural institutions, emergent properties of collective behavior, or labor market situations—and that the evolution of these macro-level conditions is, at least in part, determined by shifts in aggregate fertility behavior in the population. Social interaction hence implies a micro-macro interaction in both directions: individual behavior is influenced by aggregate conditions; the latter conditions however, are not static but evolve cumulatively through the behavior of individuals via a feedback loop. According to this definition, social interaction entails personal as well as impersonal interactions. In the former case, contacts among individuals exert influences on fertility decision, as for instance through peer pressure. In the latter case, the influences of other persons on an individual's fertility decisions are mediated through more abstract institutions, as for instance social norms, labor markets or media.
This definition of social interaction is therefore slightly more general than our earlier chapters which have focused on social