Washington ? Hoping to avoid divorce? It helps if you’re wealthy, religious, college-educated and at least 20 years old when you tie the knot. Couples who don’t live together before marriage have a better shot at staying together, as do those whose parents stayed married.

By age 30, three in four women have been married, but many of those unions dissolve. Overall, 43 percent of marriages break up within 15 years, according to a government survey of 11,000 women that offers the most detailed look at cohabitation, marriage and divorce ever produced.

Black women were most likely to divorce, with more than half splitting within 15 years. Asian marriages are the most stable, with whites and Hispanics in between.

Cohabitation factor

Women are waiting longer to get married than they used to, and after a divorce, they are less likely to remarry than women once were.

At the same time, couples are more likely to live together without marriage: Half of U.S. women had lived with a partner by the time they turned 30.

The survey, released Wednesday by the Centers for Disease Control and Prevention, found that 70 percent of those who lived together for at least five years did eventually walk down the aisle.

But these marriages are also more likely to break up. After 10 years, 40 percent of couples who had lived together before marriage had broken up. That compares with 31 percent of those who did not live together first.

That’s partly because people who choose to live together tend to be younger, less religious or have other qualities that put them at risk for divorce, said Catherine Cohan, assistant professor of human development and family studies at Penn State University. But that may not fully explain it, she said.

“Many people enter a cohabiting relationship where the deal is, ‘If this doesn’t work out we can split up and it’s no big loss because we don’t have a legal commitment,”‘ she said. “The commitment is tenuous, and that tenuous commitment might carry over into marriage.”

Still, many believe that living together is an essential testing period for a relationship.

“Most couples who decide to move in together do so because they take marriage very, very seriously. They want to be absolutely sure this is the right person before they say, ‘I do’ for a lifetime,” said Dorian Solot, executive director of the Boston-based Alternatives to Marriage Project.

But she added that expectations better be the same.

“If one of you thinks you’re headed for the altar and the other thinks you’re just splitting the cost of rent, you’re both in for a surprise,” she said.

Risk groups

The report, based on 1995 data, found other groups facing a high risk of divorce, including:

Young people. Nearly half of those who marry under age 18 and 40 percent under age 20 get divorced. Over age 25, it’s just 24 percent. The difference is maturity, says Chicago psychologist Kate Wachs.

“A lot of young people focus on right now, and if I’m not happy right now, I should get divorced,” said Wachs, author of “Relationships for Dummies.” Older people have more life experience and realize “if I hang in there, it will probably get better.”

Nonreligious people. Of those who don’t affiliate with any religious group, 46 percent were divorced within 10 years.

Children of divorce. Women whose parents were divorced are significantly more likely to divorce themselves, with 43 percent splitting after 10 years. Among those whose parents stayed together, the divorce rate was just 29 percent.

Children. Half of women who had children before marriage were divorced in 10 years. Nearly as many couples who never had children also wound up divorced.

Across the board, black women were less likely to marry and more likely to divorce. By age 30, 81 percent of white women have been married, vs. 52 percent of black women.

The report suggests part of the problem is a lack of men in the “marriageable pool,” with disproportionate numbers of black men unemployed or incarcerated. People with low-incomes are also less likely to marry, and blacks tend to have lower incomes.