08/29/2013 01:23 pm ET Updated Oct 29, 2013

Reasons for the Surge in Births to Single Women

Throughout Europe, births to single mothers more than doubled between 1990 and 2010 (from 17.4 to 38.3 percent). Imagine if it were to increase at the same rate for the next two decades! Such rapid changes are very unusual historically. They cry out for explanation from social scientists.

This steep rise in single parenthood is found in most developed countries, including the U.S. Here, single parenthood increased from around 5.3 percent in 1960 to 41 percent in 2009.

The surge in single parenthood in Europe
Change was even more rapid in some European countries. Births outside marriage increased by a factor of 21 in Ireland between 1960 and 2011 (from 1.6 to 33.7 percent) and a factor of 23 in Belgium (from 2.1 to 49.2 percent). These are not the most rapid growth rates either. Single parenthood increased by a factor of 32 in the Netherlands (1.4 to 45.3 percent) and Malta (0.7 to 22.7 percent).

Nor is the growth in births to single women likely to stabilize at these levels. In some countries the proportion of non marital births exceeds marital ones. These include Bulgaria (56.1), Estonia (59.7), Slovenia (56.8), Sweden (54.3) and Norway (55).

Plausible reasons for the surge in non-marital childbearing
Perhaps the simplest reason is the decline in marriage. The average age at marriage for women increased worldwide from 23 to 29 between 1970 and 2005, reflecting greater entry by women into higher education, paid employment, and careers.

Women are marrying later and their marriages are much more likely to end in divorce. Of course, more women are forgoing marriage altogether. So women spend far less of their reproductive lives in the married state and are thus have a lower statistical probability of producing children in marriage just as people who drive less miles have fewer accidents.

According to my unpublished analysis of 35 countries in the Eurostat database, low marriage rates account for 45 percent of the differences in out-of-wedlock births. There are also economic explanations for single parenthood.

Economic reasons
Poor women in the U.S. constitute most of the single mothers whereas there has been a negligible increase in non-marital births to middle-class women (4). This phenomenon is fairly easily explained in terms of declining wages for unskilled workers. Poor men no longer earn enough to be economically qualified for marriage and single women raise children with the help of their relatives instead.

Circumstances are quite different in Europe, however, and the surge in non-marital births is not due to increased poverty there. Indeed, thanks to a well-developed welfare state, there is little poverty in countries like Sweden that have high single-parenthood ratios.

Despite low poverty rates, welfare states may increase single parenthood by reducing marriage rates. Mothers are so well protected by the welfare state that being married provides little further economic advantage. They are better able to raise children independently if they so wish.

Female breadwinners
The period of rapidly rising single parenthood in developed countries was accompanied by a steady rise in female labor participation and enrollment in higher education. Moreover, my analysis of Eurostat data found that female labor participation rates accounted for 48 percent of the country differences in proportion of births outside wedlock (an effect that was independent of the marriage rate).

Why might single motherhood increase with the number of women participating in the labor force given that this reduces poverty? One obvious connection is that obtaining an education and getting established in an occupation takes time and postpones marriage. Another is that women who earn as much as men do not have to depend on a husband to raise a child although most might prefer not to bear the burden alone.

Either way, it seems clear that single parenthood is no longer associated with poverty in Europe (as it is in the U.S.) given that more than half of births are to single mothers in some countries.

Given the changes in Europe over the past half-century, marital births could virtually disappear in some countries in another 50 years. That prospect might seem as outrageous as claiming that atheism would replace religion (as I argue in a recent book, Why Atheism Will Replace Religion).

Yet formerly very religious countries, such as Ireland are now predominantly secular. Births to single mothers also outnumber marital births in several countries. Both types of change mirror economic development.