THE CENSUS Bureau reported yesterday that incomes were up and poverty was down last year, and politicians, led by the president, basked in the glow. But as ever with these figures, even the good news came with asterisks. The economy is in its ninth year of steady expansion with low inflation, and still an eighth of the population lives in what the government defines as poverty. For children, the figure remains near a fifth. The degree of income inequality remained essentially unchanged last year, at the highest level ever recorded.

Real median household income finally returned to, and surpassed, the peak it reached in 1989. The median rose for all income quintiles, the poorest fifth as well as the best-off. The poverty rate was the lowest since 1979; its rate has now fallen five years in a row.

Even so, as conventionally measured it was 12.7 percent; who wants to cheer for that? Among children, it was 18.9 percent; for both blacks and Hispanics, a little over 25 percent. The poorest fifth of all households had, together, 3.6 percent of household income; the richest fifth, 49.2 percent.

The figures were scanned by both sides for evidence of the effects of welfare reform. Part of the problem is separating out the effects of reform from the broader trends in the economy. More low-income mothers are working, but many are working for very low wages. The number of families with children headed by someone working year-round full-time but nonetheless living below the poverty line was the highest in the quarter-century the figure has been kept, and the bureau noted that "despite the drop in child poverty, children under age six . . . living in families with a female householder and no husband present experienced a poverty rate of 54.8 percent."

Some of the presidential candidates have indicated they may make an issue next year of the persistence of poverty and income inequality amid the general prosperity. They should. To some extent, of course, the issue never sleeps. The government is involved in the distribution of income. The president vetoed the recent tax bill in part on grounds that it was tilted toward the rich; Congress is considering an increase in the minimum wage mainly as a device to lift the incomes of the poor. Yesterday's qualified good news creates no room for complacency in that regard.