Supplementary materials to: Geographic variation in personality is associated with fertility across the United States

Levels of fertility and the shape of the age-specific fertility schedule vary substantially across U.S. regions with some states having peak fertility relatively early and others relatively late. Structural institutions or economic factors partly explain these heterogeneous patterns, but regional differences in personality might also contribute to regional differences in fertility. Here, we evaluated whether variation in extraversion, agreeableness, conscientiousness, neuroticism, and openness to experience measured at the U.S. state-level was associated with the level, timing, and context of fertility across states above and beyond sociodemographics, voting behavior, and religiosity. Generally, states with higher levels of agreeableness and conscientiousness had more traditional fertility patterns, and states with higher levels of neuroticism and openness had more nontraditional fertility patterns, even after controlling for established correlates of fertility (r ~ |.50|). Personality is an overlooked correlate that can be leveraged to understand the existence and persistence of fertility differentials.