This is a man’s world? Changes in income predict sex ratio at birth

Ohto Kanninen, Labour Institute for Economic Research, Finland
Aleksi Karhula, University of Turku

The human sex ratio at birth (SRB) is approximately 107 boys for every 100 girls. SRB was rising until the World War II and has been declining slightly after the 1950s in several industrial countries. Recent studies have shown that SRB varies according to exposure to disasters and socioeconomic conditions. However, it remains unknown whether changes in SRB can be explained by observable macro-level socioeconomic variables across multiple years and countries. Here we show that changes in disposable income at the macro level positively predict SRB in OECD countries. A one standard deviation increase in the change of disposable income is associated with an increase of 1.03 male births per 1000 female births. This is the first evidence to show that economic and social conditions influence SRB across countries at the macro level. This calls for further research on the effects of societal conditions on general characteristics at birth.