Social contagion effects in fertility: theory and analytical strategy

A vast body of research has emphasized the role of social networks and diffusion processes in the adoption of “new” demographic behavior, such as the reduction of fertility to below replacement levels, as part of the demographic transition. Diffusion theories integrate the role of individual behavior in explaining macro-level changes but, until very recently, empirical evidence at the micro level was scarce. Recent studies showed the existence of social contagion effects on fertility timing in contemporary population among siblings, friends and coworkers. Humans are social actors who make decisions and act while embedded in a web of social relationships with kin and peers, and sociologists and demographers have increasingly been acknowledging the role of interpersonal interactions in shaping fertility decision making. In this piece of work, we review the main mechanisms and processes through which fertility behavior may become contagious among relevant others, such as friends, kin, and coworkers. In doing so, we highlight the main sociological theories explaining the diffusion phenomenon at the micro-level, as well as the challenges deriving from the difficulty of disentangling “pure” social interaction effects from selection and contextual effects. The relevance of this identification problem is evident in the active and large debate on possible empirical strategies to disentangle confounding effects from diffusion. We also provide a useful overview of the existent data suitable to analyze peer effect on fertility, and discuss the potential use of big data.