LAST TUESDAY, Charles Oldham, 19, was at 500 C Street NW, the District's unemployment center, by 9 a.m. Mr. Oldham has given up job hunting in the city. He says it is a waste of time. "What's there to find [in the way of jobs]?" he asks. "Not much." The reason for Mr. Oldham's pessimism is that he is an unskilled worker. And in the District's economy, an unskilled worker has few opportunities for legal employment. Mr. Oldham is a high school graduate (Cardozo, class of '78), but he has never held any job other than as a counter clerk at a McDonald's. He says there are some job possibilities outside the District, but most would require him to have a car -- night jobs, say -- or to spend several hours every day on public transportation.

Mr. Oldham, who has been unemployed for a year, represents part of the 6.7 percent unemployment rate for all District workers. That figure is down from a year ago when unemployment reached 7.5 percent.But, paradoxically, as the unemployment rate here goes down -- even as it rises in the rest of the nation -- Mr. Oldham's chances of finding a job here are worse than ever. The reason is that not only is Mr. Oldham an unskilled worker but he is a black male between the ages of 18 and 20. The unemployment rate for people in that category in the country was 33.5 percent during 1979. In the District, the rate of unemployment for that group was worse: 39.7 percent. Why are the odds so great against black males' finding employment in the District?

Part of the answer comes in a report from the Greater Washington Research Center. The report, prepared by the center's executive vice president, Atlee Shidler, shows that the Washington job market is becoming sharply skewed toward the white-collar professions. The number of blue-collar jobs in the city is actually declining. For an unskilled person with only a high school education, such as Mr. Oldham, this means that the job market here is nearly impenetrable. And, ironically, the job market and local economy are actually growing while the blue-collar job market disappears because of the rapid growth in the number of white-collar jobs. This makes for social troubles as well as bad employment figures.

Consider that, while the number of households with incomes of over $35,000 has increased by 230 percent in the past 10 years, the number with incomes lower than $10,000 has also increased. The number of affluent people grows. And increasingly the two live near each other, creating a situation filled with tension.

The research center's report makes two suggestions for improving the employment picture for unskilled workers. The first is that increased training and education be offered to young people to enable them to become skilled workers and possibly take advantage of the rising number of white-collar jobs. The second is mounting an effort to attract blue-collar industries to the city. Neither strategy is independent of the other. Each is worthy of pursuit. But who will do it?

The leading employer in the city, the federal government, plays little or no role in promoting the local area or offering training programs to unskilled workers. As a result, the research center concludes that the local business community will have to take the lead in bringing industry to the District. But the local government must also be included in that formula. The appointment of Ivanhoe Donaldson, a close adviser to the mayor, to head the city's troubled Department of Employment Services (the labor department) is a sign of hope that the city government will be making an effort to help unskilled workers. But over the long run the city government must develop some strategy, in connection with the business community, to make it clear that the District is hungry for industry to make its home here. The future well-being of the city depends on it.