Evaluating Fluctuations in National Sex Ratios in Selected Countries: 1960s - 2012

Michele Steinmetz, U.S. Census Bureau
Heather King, Georgia State University
Barbara A. Anderson, University of Michigan
J. Gregory Robinson, U.S. Census Bureau
Wendie Choudary, University at Albany, State University of New York (SUNY)

Traditionally, national sex ratios at birth in developed countries tended to fluctuate very little. However, fluctuation can be observed when examining the age of mother and parity in national level data. This paper expands earlier work examining fluctuations in sex ratios at birth in sub-national geographies and compares trends in sex ratios at birth across countries by age of mother and parity. Using a theoretical model to calculate probability ranges of sex ratios at birth, this research examines how well data on live births from the mid-to- late 20th century through 2012 from the United States, South Korea, Denmark, Sweden, and the Netherlands matched the model’s probability ranges. Initial findings indicate the model provides insight into what is expected or “normal” fluctuation in sex ratios at birth. Such models can be a valuable research and evaluation tool, providing additional insight into changes in fertility trends in various countries.