[영문]Within societies, there is a well-established relation between socioeconomic position and a wide range of outcomes related to well-being, and this relation is known to vary in magnitude across countries. Using a large sample of nations, the authors explored whether differences in social policies explain differences in socioeconomic gradients across nations. Analyses were conducted on reading literacy in 15-year-olds, as an outcome related to cognitive development and to a host of factors that contribute to future well-being, including educational attainment and health. The results show a systematic variation in socioeconomic gradients and average scores across countries. Scores were favorable in countries with a long history of welfare state regimes, but countries where institutional change unfolded more recently and rapidly, or where welfare states are less well developed, clustered at the bottom of the rankings. Strong support was found for the qqqquot;flattening upqqqquot; hypothesis, which suggests that nations with higher average scores have less socioeconomic inequality in scores (or flatter gradients). Potential explanations for the observed patterns include differences between nations in the extent and distribution of income and social goods important for children's development.