Partner plus children = happiness? The effects of partnerships and fertility on well-being

Economic and rational-choice theories suggest that individuals form unions or have children because these decisions increase their subjective well-being or "happiness." We investigate this relation using within-MZ (identical) twin pair estimates to control for unobserved factors, such as optimistic preferences, that may simultaneously affect happiness, partnerships, and fertility. Our findings, based on Danish twins aged 25-45 and 50-70 years old, include the following. (1) Currently being in a partnership has large positive effects on happiness. (2) A first child substantially increases well-being, in analyses without controls for partnerships, and males enjoy an almost 75 percent larger happiness gain from a first-born son than from a first-born daughter; however, only females enjoy a happiness gain from the first-born child with controls for partnerships. (3) Additional children beyond the first child have a negative effect on subjective well-being for females, while there is no effect for males. (4) Ever having had children does not significantly affect the subjective well-being of males or females aged 50-70 years.