Using a large special study population and refined indicators of socio-economic status, the relationship of the live birth sex ratio to socio economic variables is examined. The analyses provide control for the possible confounding effects of race and birth order.
The sex ratio is shown to be significantly and positively associated with socio-economic variables. The relationship is not linear, however, but instead is characterized by an apparent ‘diminishing returns’ curve. The major increase in sex ratio is detected as socio-economic status increases from low to moderate. No significant change occurs between moderate and higher socio-economic levels.
Even after controlling for the significant socio-economic effect, the analyses detect a significant difference between the sex ratios of Whites on the one hand and Negroes and Puerto Ricans on the other.
No significant association between birth order and the sex ratio can be detected in the study population.
