Across two meta-analyses, American women's assertiveness rose and fell with their social status from 1931 to 1993. College women and high school girls' self-reports on assertiveness and dominance scales increased from 1931 to 1945, decreased from 1946 to 1967, and increased from 1968 to 1993, explaining about 14% of the variance in the trait. Women's scores have increased enough that many recent samples show no sex differences in assertiveness. Correlations with social indicators (e.g., women's educational attainment, women's median age at first marriage) confirm that women's assertiveness varies with their status and roles. Social change is thus internalized in the form of a personality trait. Men's scores do not demonstrate a significant birth cohort effect overall. The results suggest that the changing sociocultural environment for women affected their personalities, most likely beginning in childhood.