Within the first year after divorce, the standard of living of women declines 73 percent; the standard of living for men does not decline at all: it rises by 42 percent. This is one of the more startling findings of a 10-year study of divorce that began after California passed the first no-fault divorce law in 1970.

In the next dozen years, 48 other states and the District of Columbia adopted some form of no-fault divorce. By 1984, South Dakota was the only state with its traditional law unchanged. The consequences have been documented by Lenore J. Weitzman, associate professor of sociology at Stanford University, and published in a new book, "The Divorce Revolution, the Unexpected Social and Economic Consequences for Women and Children in America."

The book is based on 10 years of research, interviews with hundreds of divorce lawyers, judges, divorced men and women and an analysis of 2,500 divorce records. The results of the divorces have been, in a word, disastrous, particularly for middle-class, college-educated women.

"When I first started getting results and finding cases of women married 25, 30 and 35 years, who were losing all support, losing the family home, women who had been housewives, who had no prospects of employment, I really thought they were the exception," Weitzman said.

"They'd had the wrong attorney, the wrong judge. But as I confronted the data and we got more and more printouts from different computer samples and interview samples, and interviewing the attorneys, every single source said the same thing: divorced women are suffering extreme economic hardship."

In a typical divorce, Weitzman said, judges divide income by giving the husband two-thirds and the wife and two children one-third. If his income is $1,200, he retains $800 and three other people share $400.

Before no-fault went into effect in California, Weitzman said, one in 10 family homes had to be sold in the course of divorce. Now, one in three are forceably sold. "Judges say we have to order the home sale so we can divide the property 50-50. This means lots of moves and uprooting for children and changing schools and friends just at the point when they need stability.

"The other group suffering a lot under that rule has been the older women who have devoted themselves to their marriages. Their whole social network revolves around the home. Some of the most cruel cases have been women given 30 days to leave their home. One woman said, 'I felt as if I'd been evicted from my life.' " One way out of this, said Weitzman, is to exempt the home from the division of property.

Her argument for this goes to the very definition of property, which in the past had been home, home furnishings, cars. "Now," she said, "it's career assets, the benefits and entitlements that are linked to a person's career. In most marriages the major investments have been toward the husband's career. Increasingly, pensions are being recognized as marital property. Other forms are not being recognized. My favorite example is medical insurance. A woman who is divorced at 55 who has no insurance finds she can't get coverage," while the husband remains insured through his employment.

"If these assets are left out of the definition of property and the pool of property then the courts simply cannot be dividing property either equally or equitably. It's like saying we're going to divide the family jewels, but first we're going to give the husband all the diamonds. The diamonds are often his career assets, his pension, his license, his education, his earning capacity, his medical insurance and the other benefits of employment.

"We found the average divorcing couple has less than $20,000 in net assets," including equity in their house. "In one year the average couple can earn more than the total value of their assets. It suggests that earning capacity is worth more in one year than the total of their assets. That's why we're making such an unequal division of family property."

Women and children are the fastest growing group of poor people in the country. More than half of all children in one-parent homes are living in poverty, and current estimates are that 60 percent of the children born now will spend some of their lives in a one-parent family. Weitzman cites Census Bureau data to the effect that 40 percent of all women in their late twenties are likely to become single parents at some point in their lives.

Under the present system, they are becoming systematically impoverished, at precisely the time they need to be as stable as possible for their children. The legal system that led to the divorce revolution has unexpectedly, but methodically, created a new class of poor.