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A meta-analysis of 172 studies attempted to resolve the conflict between previous narrative reviews on whether parents make systematic differences in their rearing of boys and girls. Most effect sizes were found to be nonsignificant and small. In North American studies, the only socialization area of 19 to display a significant effect for both parents is encouragement of sex-typed activities. In other Western countries, physical punishment is applied significantly more to boys. Fathers tend to differentiate more than mothers between boys and girls. Over all socialization areas, effect size is not related to sample size or year of publication. Effect size decreases with child's age and increases with higher quality. No grouping by any of these variables changes a nonsignificant effect to a significant effect. Because little differential socialization for social behavior or abilities can be found, other factors that may explain the genesis of documented sex differences are discussed.