Birth Order's Influence on Political Attitudes and Personality

Key Insight

Birth order within families has a measurable, albeit weak but statistically significant, impact on personality traits and political orientation. First-borns receive undivided parental resources initially, leading to slightly higher IQs and a higher likelihood of achieving high rank in society, such as corporate CEOs, Nobel laureates, or political leaders; for example, seven of the eight UN Secretaries General from 1946 to 2016 were first-borns. Frank Sulloway's meta-analysis of 'Big Five' personality traits found first-borns to be more 'Conscientious' (organized, responsible, self-disciplined, traditional), a trait strongly correlated with the political right.

Later-borns, in contrast, exhibit a greater streak of rebelliousness and adventurousness. They score higher on 'Openness' (novelty-seeking, nonconformity), a trait correlating strongly with the political left. Examples of later-born rebelliousness include their overrepresentation among US presidential assassins and, in Major League baseball, younger brothers stealing or attempting to steal 10.6 times as many bases as older brothers, and being 3.2 times more successful. Later-borns were also 3.0 times more likely to circumnavigate the globe, reflecting novelty-seeking behavior and xenophilia.

Overtly political behavior also correlates with birth order. In scientific revolutions, later-borns were 3.1 times more prone to support liberal theories, and 7.3 times more so when their first-born sibling opposed the theory. On the US Supreme Court, Republican presidents nominated first-born justices twice as often as Democratic presidents, and first-borns were significantly more likely to vote with the majority in divided landmark cases. Studies on contemporary issues show later-born high school students were more likely to use marijuana (a form of 'rebelliousness against the status quo'), and later-born college students were more likely to participate in civil disobedience. Japanese American first-borns were 1.4 times more likely to vote for conservative candidates. Overall, later-borns are estimated to be between 20% and 43% more likely than first-borns to support liberal political positions, candidates, or social causes, as seen in the public ideological clash between Ecuador's left-wing President Rafael Correa (younger brother) and his more conservative older brother, Fabricio.