But perhaps the strongest support for Eberstadt’s Family Factor is the baby boom. Most people know that, in the two decades following World War II, birth rates across the West shot up and remained elevated for an entire generation. What fewer people know is that the baby boom was powered, in part, by a sharp increase in marriage rates, too. But what very few people realize is that the baby boom also witnessed a marked increase in religiosity across the West, with church membership and attendance both spiking for a generation.

Sociologists have long been flummoxed by the baby boom; there is no fully satisfying explanation for why it happened. Eberstadt suggests that we can’t understand it apart from the religious revival which accompanied it. Because, just as religion fosters family life, family life is a conduit to religion. The two form what Eberstadt evocatively proposes is a “double-helix,” supporting and influencing one another.

How the West Really Lost God doesn’t provide conclusive proof of the existence of a Family Factor; Eberstadt isn’t toiling in the minutiae of econometric regression analyses. What she’s done is construct a fascinating work of forensic demography which manages to take the telescope through which we’ve long studied the relationship between family formation and religiosity and flip it entirely around to let us peer through the other side.