Quantifying Social Construction: Evidence from blood type discrimination in Japan

Recent trends in populism have revived essentialist views on human traits, prompting renewed debates about whether prejudices are biologically determined or socially constructed. Although previous studies have demonstrated the socially constructed nature of many prejudices, the long history of socioeconomic and political oppression makes it challenging to pinpoint the specific biases that drive discrimination. I address this issue by leveraging a unique natural experiment: discrimination based on blood type in Japan's marriage and labor markets. Specifically, I quantify how the arbitrary prejudice that labels individuals with type B blood as selfish leads to tangible discrimination. I develop a novel theoretical framework to differentiate direct, taste-based discrimination from indirect, market-based discrimination that operates through diminished labor market prospects and self-fulfilling prophecies. Empirical results reveal that this bias reduces marriage rates by 5.4 percentage points and increases unemployment rates by 2 percentage points, with additional evidence highlighting self-fulfilling prophecies among Japanese men with type B blood. The findings underscore the significant economic impact of a particular, socially constructed prejudice.