Throughout most of history, starting a family was a task that most people either aspired to or dutifully performed. Today, that is increasingly not the case—not only in Europe, Japan, Australia, or North America, but in the world’s most economically dynamic region, East Asia. The trend towards post-familialism, a society in which the family and marriage are no longer central to society, will reshape our politics, economy, and society in the decades ahead.

Postwar baby boomers, born between 1946 and 1964, were Generation Zero for the Second Demographic Transition in the United States. Now shuffling their way into their sixties and seventies, older boomers give a glimpse of the long-term downside of the post-SDT culture. If we had to pick just one word to describe it, “lonely” would do. In widely quoted research published in the Proceedings of the National Academy of Sciences, Ashton M. Verdery and Rachel Margolis uncovered a recent surge in the number of “kinless” older adults. Lower fertility translates into fewer siblings, aunts, uncles, and cousins, whether for hospital visits or emergency contacts.