Arguments about the spread of gender egalitarian values through the population highlight several sources of change. First, structural arguments point to increases in the proportion of women with high education, jobs with good pay, commitment to careers outside the family, and direct interests in gender equality. Second, value shift arguments contend that gender norms change with social and economic development among women and men in diverse positions--traditional and non-traditional alike. Third, diffusion arguments suggest that structural change leads to adoption of new ideas and values supportive of gender equality by non-traditional and innovative groups in society, but that the new ideas later diffuse to other groups through cultural processes. Using the General Social Survey from 1977 to 2006 and comparing the determinants of gender egalitarianism across 86 cohorts born from roughly 1900 through 1985 time frame, multilevel models support the diffusion arguments. (Contains 1 figure, 2 tables and 7 notes.)