Media Briefings


  • Published Date: March 2013

A scarcity of men relative to women can lead to an increase in the proportion of children born to unmarried mothers. That is the central finding of research by Dirk Bethmann and Michael Kvasnicka, published in the March 2013 issue of the Economic Journal.

Their study looks at the experience of Germany shortly after the Second World War, where there were only two men for every three women in the 20-40 age group, as a result of military casualties and soldiers being missing in action or prisoners of war (POWs). At the same time, the share of children born out of wedlock, which had been less than 10% before the war, had risen to more than 16%.

The researchers conjecture that the war-induced squeeze faced by women in the ‘marriage market’ was responsible for the dramatic rise in the out-of-wedlock birth ratio. In the low sex ratio environment after the war, mating opportunities for men were relatively abundant and those for women were relatively scarce.

These unequal opportunities changed the respective bargaining power of men and women in the marriage market. Women, the authors argue, are likely to have found it more difficult to secure long-term male commitment in the form of marriage, both when pregnant and more generally as a precondition for maintaining or engaging in a sexual relationship.

To test their hypothesis, Bethmann and Kvasnicka gathered historical data for more than 160 counties in Bavaria from different archives, statistical offices and libraries. The data show that the male shortfall varied across counties. The two researchers use these variations across counties to measure the influence of the male shortfall on out-of-wedlock childbearing.

Their analysis shows that the war-induced falls in sex ratios at the level of counties led to significant increases in the respective out-of-wedlock birth ratios.

A further important finding is that the effect of a decline in the sex ratio on the out-of-wedlock birth ratio depended in magnitude on the nature – and hence the permanence – of the male shortfall in a county. The effect on the out-of-wedlock birth ratio was stronger when the male shortfall was mainly driven by military deaths and missing soldiers; it was smaller when caused more by POWs.

Unlike soldiers who had died in combat or were missing in action after the war, POWs had a significant chance of returning home. This meant that counties with a larger relative population of prisoners in the immediate aftermath of the war could expect to see a greater future improvement in women’s marriage chances.

In anticipation of this development, women may have postponed fertility decisions. At the same time, men were probably more prepared to bind themselves by marriage to a partner. This reduced the frequency of out-of-wedlock births.

These findings may be of general importance for studies of the effects of sex ratio imbalances on economic, social and demographic outcomes. Future changes in marriage market conditions may differ in other settings across regions and groups of individuals in important ways that can be anticipated. If so, then restricting the focus to current measures of sex ratios is likely to be inadequate.


Notes for editors: 'World War II, Missing Men and Out of Wedlock Childbearing’ by
Dirk Bethmann and Michael Kvasnicka is published in the March 2013 issue of the
Economic Journal.

Dirk Bethmann is at Korea University. Michael Kvasnicka is at RWI Essen.

For further information: contact Michael Kvasnicka on +49-30-2021598-14 (email:; or RES Media Consultant Romesh Vaitilingam on +44-7768-661095 (email: