VIEWED FROM THE top of the ladder economic progress by blacks has been continuous over the past decade. Rapidly increasing numbers of well-educated young black people have been moving into the professions, business and public administration. But viewed through the income statistics for the whole population, the pattern is much less promising. The gap between the average incomes of black and white families is not being closed. It is as wide now as it was a decade ago.

Vernon E. Jordan, the president of the National Urban League, does a service in calling attention to that second and less visible reality in the league's annual report on the state of black America. Twenty years ago the median income of black families was little better than half that of white families. Ten years ago it had improved significantly, to about 61 percent of the white level. But since then, there has been no further progress at all toward equality.

Similarly, 20 ago more than half of all blacks had incomes below the federal definition of poverty. By 1970, the proportion had fallen to one-third. Since then, once again, there has been little progress. That proportion has fallen by several percentage points but, since the black population has grown, the number of black people living in poverty at the end of the decade was actually slightly larger than at its beginning. Unemployment among blacks, over the past year, has been more than twice as high as among whites. Over the last five years, the gap here has widened.

There is no mystery about this failure. In recent history there have been two periods when blacks moved rapidly closer to the national averages of prosperity. The first was World War II, with its tremendous labor shortages. The second was the 1960s, when vigorous federal social policy and tight labor markets reinforced each other. Blacks have gained most rapidly, and the cause of equality has flourished, in those times when everyone was doing well and the national economy was expanding strongly.

But the long boom of the 1960s ended in 1971. Since then, there have been two recessions and generally poor economic growth. You have heard much argument in the past few years over the desirability of economic growth. The comparison of incomes of blacks and whites contains one of the strongest arguments for continued growth. Without it, standards of living come to a standstill and the relative disparities and disadvantages are frozen.

A return to higher growth rates now probably depends first of all on this country's ability to bring down its inflation rate. The point is made by Bernard E. Anderson of the Rockefeller Foundation, who contributed the chapter on economic policy to the league's report. As long as high inflation rates persist, he observes, full employment is not likely to be sought very vigorously. The case for bringing down inflation, and speeding up economic growth, is essentially a moral one.