The effects of sex and childlessness on the association between status and reproductive output in modern society

Examining the association between socioeconomic status and reproductive output in modem societies has led to conflicting results. In this study, we used a representative sample of contemporary Swedish men and women to analyze possible reasons for the contradictory results. We found that the relationship between socioeconomic status-described here by income and highest educational level attained-and reproductive output is dependent on sex and the inclusion or exclusion of childless individuals. In men, there is a strong positive association between income/education and average offspring count if childless individuals are included in the analysis; this association is absent when such individuals are excluded. We attribute this reversal mainly to the higher proportion of childless individuals among men of lower socioeconomic background. Among other factors, female choice appears to be a major cause of this association because the proportion of men who never married increased, with decreasing income category and educational level. In women, however, including and excluding childless individuals both yielded a negative association between income and average offspring count as well as a null or negative relationship between education and average offspring count. (C) 2007 Elsevier Inc. All rights reserved.