This paper quantifies the causal negative impact of age on women’s marriage market appeal using an experiment where real online daters rate hypothetical profiles with randomly assigned ages. Truthfulness is incentivized through the experiment’s compensation: participants receive professional dating advice customized according to their ratings. The experiment shows that for every year a woman ages, she must earn $7, 000 more annually to remain equally attractive to potential partners. This preference appears driven by women’s asymmetric fertility decline with age, as it is present only for men without children and who have accurate knowledge of the age-fertility trade-off.

Throughout the twentieth century, the relationship between women’s human capital and men’s income was nonmonotonic: while college-educated women married richer spouses than high school–educated women, graduate-educated women married poorer spouses than college-educated women. This can be rationalized by a bidimensional matching framework where women’s human capital is negatively correlated with another valuable trait: fertility, or reproductive capital. Such a model predicts nonmonotonicity in income matching with a sufficiently high income distribution of men. A simulation of the model using US Census fertility and income data shows that it can also predict the recent transition to more assortative matching as desired family sizes have fallen.