This paper explores the causal link between income and fertility by analyzing women's fertility response to the large and permanent income shock generated by a husband's job displacement. I find that the shock reduces total fertility, suggesting that the causal effect of income on fertility is positive. A model that incorporates the time cost of children and assortative matching of spouses can simultaneously explain this result and the negative cross-sectional relationship. I also find that a husband's displacement accelerates childbearing, which is consistent with lifecycle models of fertility in which the incentive to delay is driven by expected earnings growth. (Contains 3 figures, 7 tables, and 28 footnotes.)