Robert Rector

The most useful tool in measuring the decline in marriage and the growth in illegitimacy is the illegitimacy ratio.  The illegitimacy ratio measures the number of out-of-wedlock births as a percent of all births in a year.  Thus, if there were 100 births in a society in a given year and 30 of those births were out-of-wedlock, the  illegitimacy rate or ratio would be 30 percent.

The illegitimacy ratio is important because it measures the extent to which illegitimacy is displacing marriage as the mode for bearing and raising children in our society. It is now widely recognized that illegitimacy is a profound underlying factor contributing to most other social problems.  The illegitimacy ratio is the best possible tool for indicating the potential magnitude of a wide array of future social problems.

The illegitimacy ratio, or the percentage of births that are out-of-wedlock, has expanded rapidly for both whites and blacks since the beginning of the War on Poverty in 1965.  Among whites, the out-of -wedlock birth rate has risen from 4 percent of all births in 1965 to 23.6 percent of births 1995.  Among blacks 69.9 percent of births were out-of-wedlock in 1995, up from 28 percent in 1965.

The rise in illegitimacy is propelled by three factors:

1) the decline in the portion of women of child bearing age who are married
2) the increase in the birth or fertility rate among non-married women, and
3) the decline in the birth or fertility rate among married women

The Decline in Marriage

Over the last thirty years marriage as an institution has declined in the U.S.  For example, in 1965, nearly two thirds of all women aged 20 to 24 were married; by 1993 this number had fallen to 34 percent.  Similarly, back in 1965 almost 90 percent of women aged 25 to 29 were married; by 1993 this number had shrunk to 58 percent.

The Rising Birth Rate to Unmarried Women 

The percentage of non-married women in their late teens, twenties and thirties has thus clearly grown over the last three decades.  Alarmingly, as the number of non-married women has increased, the probability that these women will have children while unmarried has also grown.  Thus, American society is now characterized by a growing number of non-married women who as a group have an increasing tendency to bear children out-of-wedlock.  In 1965 there were 23.4 births per 1,000 non-married women aged 15 to 44.   By 1995, the number had risen to 45.1.  Thus, the overall birth rate among non-married women has nearly doubled over the last 30 years.  The increase is particularly steep among young unmarried women.  Among non-married women aged 15 to 19, the birth rate per 1,000 women rose from 16.7 in 1965 to 44.4 in 1995.  Among unmarried women aged 20 to 24, the birth rate rose from 39.6 per 1,000 to 70.3 per 1,000.

The Falling Birth Rate to Married Women

While the birth rate among non-married women in the U.S. has been increasing, the birth rate among married women has gone in the opposite direction.  Thus, not only has the marriage rate among women of child bearing age declined but the birth rate among the shrinking pool of married women has also fallen.  In 1965, there were 130 births per 1000 married women.  By 1995 the birth rate of married women had been cut by a third, falling to 83.9 per 1,000.

Changes in Total Births

While the total number of births has increased since the beginning of the War on Poverty in the mid 1960’s, the number of children born to married couples has declined, falling from 3.47 million births in 1965 to 2.65 million births in 1995.  In the same period, the number of births to non-married women has quadrupled, rising from 0.29 million in 1965 to 1.25 million in 1995.

Understanding Illegitimacy

It is important not to confuse the issue of illegitimacy merely with the birth rate to non-married women, ie., births per 1000 non-married women .  As noted, the percentage of births that are out-of -wedlock is determined by three factors: the marriage rate, the birth rate of married women, and the birth rate of non-married women.  A decline in the birth rate to non-married women means little if the marriage rate and the birth rate to married women are also declining, In fact, in those circumstances, it is quite  possible for illegitimacy to rise even as the birth rate among non-married women falls.

It is also important not to confuse the issue of illegitimacy with teen pregnancy.  While teen pregnancy is very important, it is only a small part of the overall problem of illegitimacy.  Only about one tenth of all out-of wedlock births occur to girls under age 18.  Out-of wedlock childbearing occurs primarily among young adult women, with the largest number of births occurring with women aged 18 to 24.