Document Detail

Sex ratio at birth, polygyny, and fertility: a cross-national study.
MedLine Citation:
PMID:  17019835     Owner:  NLM     Status:  MEDLINE    
The sex ratio at birth may reflect frequency of intercourse that affects the timing of conception. If so, cross-national variation in polygyny and fertility might account for country differences in secondary sex ratios. Consistent with the timing of intercourse hypothesis, the birth sex ratios of 148 countries declined with total fertility rates and polygyny intensity, and increased with contraception use in correlational analysis. Regression analysis confirmed that polygyny was a negative predictor of the sex ratio (and contraception was a positive predictor), with level of economic development and mother's age controlled, but the effects disappeared with total fertility added to the equation. The sex ratio evidently declines with increases in fertility because more children are born at a later birth order when frequency of intercourse is lower.
Nigel Barber
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Social biology     Volume:  51     ISSN:  0037-766X     ISO Abbreviation:  Soc Biol     Publication Date:    2004 Spring-Summer
Date Detail:
Created Date:  2006-10-05     Completed Date:  2006-11-06     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0205621     Medline TA:  Soc Biol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  71-7     Citation Subset:  IM    
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MeSH Terms
Birth Order
Contraception / utilization*
Cross-Cultural Comparison
Interviews as Topic
Marriage / ethnology,  statistics & numerical data*
Maternal Age
Parturition / ethnology*
Sex Factors
Sex Ratio*
Time Factors

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