There is an extensive literature discussing how individuals’ marriage behavior changes as a country develops. However, no existing data set allows an explicit investigation of the relationship between marriage and economic development. In this paper, we construct new cross-country panel data on marital statistics for 16 OECD countries from 1900 to 2000, in order to analyze such a relationship. We use this data set, together with cross-country data on real GDP per capita and the value added share of agriculture, manufacturing, and services sectors, to document two novel stylized facts. First, the fraction of a country’s population that is married displays a hump-shaped relationship with the level of real GDP per capita. Second, the fraction of the married correlates positively with the share of manufacturing in GDP. We conclude that the stage of economic development of a country is a key factor that affects individuals’ family formation decisions.