Abstract: The ratio of males to females in a population has been shown to influence behavior in both animals and humans. Building on theories in evolutionary psychology and empirical studies in relevant fields, we summarize the effects of sex ratio on human behavior in six categories: sex selection, mating, marriage, parental investment, aggressive behavior, and economic behavior. This topic may be especially relevant to the Chinese context, due to the growing tendency for males to outnumber females in Chinese society. Therefore, a comprehensive understanding of how and why sex ratio influences individuals’ psychology and behavior, especially among Chinese population, has the potential to shed light on a number of important social issues.

Key words: sex ratio, operational sex ratio, mating, sex selection, economic behavior