Progress in the attempt to abolish poverty in America has come to a halt, and there is somewhat more destitution now than 15 years ago, says a study of the nation's urban underclass that uncovered some unexpected results.

Poverty lingers, with the condition shared at any given time by 13 percent of the population, but the big change is in its uneven nature, according to "The Urban Underclass" issued by the private Brookings Institution at a conference Tuesday.The study found that white people and older people are less impoverished than in the past, but young families, especially those with no father present, are more likely to be poor.

For blacks, the story is stagnation: 31 percent were poor in 1967, 31 percent are poor now.

Digging beyond the statistics, sociologist Christopher Jencks of Northwestern University looked at eight aspects of the underclass and found:

-Two problems that "have gotten steadily worse" are joblessness among men and unwed parenthood.

Long-term joblessness rose in both the 1970s and 1980s. Blacks who once worked sporadically have "often withdrawn from the labor force" as work for the unskilled has disappeared.

Babies without fathers at home are increasing both because of out-of-wedlock births and divorce.

-Two problems that "have stopped getting worse" are welfare and violence.

The proportion of single mothers collecting welfare has leveled off since 1974. Violent crime is less common than it was 10 or 20 years ago, especially among blacks.

-Two problems that "have gotten steadily better" are dropout rates and reading and mathematics skills.

More whites and blacks are likely to earn a high school diploma or an equivalency certificate than at any time in the past. The proportion of 17-year-olds with basic reading skills has risen and young blacks have improved their math skills.

-Two problems that "have stopped getting better" are teenage parenthood and poverty.

Teenage motherhood declined during the 1960s and 1970s, then stabilized. Families and individuals with below poverty-level incomes fell steadily between 1940 and 1970, but has not changed much since.

By any measure, overall poverty has climbed slightly between 1974 and 1988, the latest year for which statistics were available, Jencks said. Lyndon Johnson's "war on poverty" in the late 1960s did not achieve its purpose, but it was not a failure, said Paul Peterson, director of the Center for American Political Studies at Harvard University.

The effort especially helped the elderly, bringing them low-cost medical services and greatly improved retirement benefits, Peterson said. It also boosted cash assistance to the blind, deaf and disabled.

But "young families have experienced a steadily increasing chance of being poor," Peterson said. "The probability that a child under the age of 18 would be living in a poor family increased from 15 (percent) to 20 percent" between 1970 and 1986.

Jencks challenged the conventional belief that teenage pregnancies among black girls have become an epidemic. During the 1980s, he said, "teenage girls were having fewer babies than at any time since 1940."

While 80 out of 100 black girls gave birth before age 20 in 1960, the figure fell to 51 out of 100 by 1986, he said. Among white girls, the figures declined from 40 to 21 of 100.