As sex ratio imbalances have become a problem in an increasing number of countries, it is important to understand their consequences. With the defeat of the Kuomintang Party in China, more than one million soldiers and civilians, mainly young males, retreated to Taiwan in the late 1940s. Initially, the soldiers from mainland China were not allowed to marry. The ban was relaxed in 1959, however, suddenly flooding the marriage market with a large number of eligible bachelors. The operational ratio of males to females at marriageable age peaked at nearly 1.2 in the 1960s. Using data from multiple sources, we find that during times of high marriage competition, young men are more likely to become entrepreneurs, work longer hours, save more, and amass more assets. The findings highlight the important role of biological forces in shaping human economic behavior.