RESUMO
Historically, family ties have been understood as the primary source of support for aging adults, and past empirical and theoretical work has highlighted the tendency of older adults to focus on close family. However, in line with demographic changes and historical increases in the diversity of social structures, friendships are increasing in importance in recent generations of older adults. Given the powerful role of context in shaping these changes, this paper offers a conceptual analysis linking individual agency to sociohistorical context as a way to understand this increasing diversity of social ties. More specifically, we propose that the individual invests time and energy to form and maintain social ties, and that each individual has a specific social opportunity structure (all potential ties that are available to invest in, as well as the costs of those investments). Furthermore, this investment of time and energy is determined in part by individual differences in capacities and motivations. We argue that sociohistorical context influences this process in three important ways: (1) in its effect on the social opportunity structure; (2) in its direct effect on time and energy; and (3) in its effect on individuals' capacities and motivations. We believe that these mechanisms can account for the increasing diversity of social ties across adulthood, as well as the potential for future historical changes.