The effect of masculinization of births on the marriage market

The majority of the world’s population has been male since 1955. The proportion of males has been rising slightly since that time primarily due to imbalances in Asia. In the 1990s an abnormal increase in the proportion of male births was also observed in several countries throughout the world.


In India the sex ratio at birth is 110 boys for 100 girls and in China, 115/100, whereas the norm is 105/100. Even if this ratio were to return to normal quickly in the two countries, they would continue to have a majority of men to the end of the century. One mechanical effect of the current deficit in female births is to reduce the number of adult women and therefore of future births.

 Among adults, masculinization causes imbalance on the heterosexual marriage market (or “marriage squeeze”) and in family formation mechanisms. For example, the surplus of men of marrying age in China will rise by approximately 1.3 million annually over the next twenty years, amounting in 2041 to a total excess of 41 million men over age 22.

By 2050 in China and India, the number of single men seeking to marry is expected to exceed the number of eligible women by over 50%. This suggests the degree of marriage market saturation.

What does all this mean for the demography of the future?

  • Due to the cumulative effect of sex ratio at birth imbalances on the marriage market, the marriage squeeze will be considerably higher than simple age structure comparisons indicate. Current cohorts of future husbands, men who are marrying at later ages, are larger than those of their potential future wives since these men were born several years before the women and in larger cohorts.
  • Returning to a normal sex ratio at birth will not end the marriage squeeze because there is a backlog of earlier cohorts; i.e., a gradual accumulation of single men on the marriage market. For each period, not only new arrivals but also men who have not yet found a wife have to be taken into account.
  • An increase in spousal age difference would considerably reduce marriage market squeeze, while a rise in the number of single women would have the opposite effect.
  • The surpluses of single men expected in China and India are so great that easing the problem significantly through international migration does not seem plausible.

These developments seem to be leading countries with patrilineal traditions into an entirely unprecedented situation: some of the male children parents so ardently wished for today may well be unable to marry in the future—and therefore to perpetuate the family line—simply because there are too many of them. In other words, this regime does not seem demographically sustainable, and in the long term prenatal selection of boys is expected to undermine the foundations of patrilineal systems founded on family reproduction through the male line.

Source: Christophe Z. Guilmoto (2015), The Masculinization of Births. Overview and Current Knowledge, Population, 70 (2)

Contact: Christophe Z. Guilmoto

Online: August 2015