About half of first marriages in the U.S. are likely to survive at least 20 years, according to government estimates. But for one demographic group, marriages last longer than most: College-educated women have an almost eight-in-ten chance of still being married after two decades.

Researchers at the National Center for Health Statistics estimate that 78% of college-educated women who married for the first time between 2006 and 2010 could expect their marriages to last at least 20 years. But among women who have a high school education or less, the share is only 40%.

The probability of a lasting first marriage is derived from marital history data from the National Survey of Family Growth, a nationally representative sample of women and men who were ages 15 to 44 between 2006 and 2010. Estimates are based on an approach similar to that used to determine life expectancy and assume that marriage patterns in the future will follow patterns today. The findings refer only to opposite-sex marriages; the sample size was too small to analyze same-sex marriages.

Reasons for marriages ending include divorce and separation. Marriages that ended in death were not included in the analysis. One limitation of the survey was that it did not include adults over age 44 and therefore does not take into account long-term marriages that started later in life. And adults with advanced degrees were not separately analyzed because of the small sample size.

The findings are yet further evidence of the marriage gap in the U.S. along educational lines. College-educated adults are more likely to be married than less-educated adults. Among those who were ages 25 and older in 2014, 65% of those with a bachelor’s degree or more were married, compared with 53% of adults with less education, according to a Pew Research Center analysis.

While the research does not address reasons these marriages last longer, we do know college-educated adults marry later in life and are more financially secure than less-educated adults.

While more-educated women have the highest chances for a long-term marriage, college-educated men also stand out. Roughly two-thirds (65%) of men with a bachelor’s degree could expect that, if they marry, their first marriage will last 20 years or longer, compared with 50% of men with a high school diploma or less. In addition, men with a higher level of education are more likely to get married in the first place when compared with less-educated men.

There also are distinctive patterns in marriage longevity by race and ethnicity. Some of these differences could be related to educational differences among adults with different racial or ethnic backgrounds. Asian women, who are among the most educated, are more likely than any other racial or ethnic group to have a long-term marriage. For Asian women who were married for the first time between 2006 and 2010, the chance that they may celebrate their 20-year wedding anniversary is nearly 70%. By contrast, about half of Hispanic and white women may see their marriages last that long. And for black women, the chance is 37%.

Among men, Hispanics have the highest likelihood of being in a long-lasting marriage (findings about Asian men are not included because the sample size was too small to be nationally representative). For those who married for the first time between 2006 and 2010, about six-in-ten Hispanic men (62%) could expect their marriages to last at least 20 years, compared with 54% of white men and 53% of black men.

Another factor linked to long-lasting marriages is whether couples live together before tying the knot. In short, couples who lived together before getting married had a slightly lower chance of having a long-term marriage than those who did not live together.

Among women who did not live with their spouse before getting married for the first time, 57% can expect to still be married after 20 years. For women who lived with their spouse before marriage, the probability of being married for at least 20 years is somewhat lower – 46%. Whether the couple was engaged when they lived together didn’t make a difference in women’s chances of long-lasting marriages.

For men, the patterns are slightly different. In this case, it matters whether men are engaged to a partner they lived with before getting married. Men who lived with their future spouse without being engaged had a slightly lower chance of having a long-term marriage (49%) than those who were engaged first (57%). Men who didn’t live with their partner before getting married had a 60% chance of celebrating their 20th anniversary.