"Whatever else is to be said about war, it makes social statistics look good," Daniel Patrick Moynihan once wrote of the war in Vietnam.

Moynihan, now a Democratic senator from New York, has a knack for over-generalizing, but he was right about Vietnam. As much as any other factor, the war boom accounted for the rapid economic progress of blacks during the 1960s. It created employment, allowed blacks to move to higher-paid jobs and eased the tension between blacks and whites competing for work.

The experience of the 1960s is a sobering reminder that much of history is accidental. With the black unemployment rate still more than twice the white. President Carter's challenge now is to do purposefully what the war did incidentally. It won't be easy.

For just as the war created its own realities. Carter remains at the mercy of realities that cannot be changed easily: decaying central cities, an inflationary economy and an increasingly ungenerous political climate. People are worried about maintaining their own living standards, not paying extra taxes to imporove somebody else's.

Yet these is litte doubt that the 1970s have treated blacks more hashly economically than whites. A few comparisons make this vividly clear.

First, employment. In the 1974-75 recession, black employment began declining earlier than white and went down further. Now, it has rebounded less. For whites, the pre-recession peak in employment occurred in July 1974, but blacks reached their peak seven months earlier. At the recession's low, white employment had declined 2.1 per cent from this peak. For blacks the decline was 5.3 per cent. Finally, white employment (81 million in September) now stands about 5.3 per cent about the pre-recession peak. Black employment (at 9.7 million) exceeds the pre-recession peak only 4.4 per cent.

Second, income. According to the latest, Census Bureau report, median black family income in 1976 was only 59.5 per cent of white family incom, slightly less than the 61 per cent in 1969. All through the 1960s, black had gained; in 1959, for example, the ratio of median incomes was only 51 to 100. Although both black and white median incomes - expressed in constant 1976 dollars, climinating the effect of inflation - remain below their previous peaks, white income now appears to be rising strongly. In 1976, the median family income of $15,537 was up about 3 per cent over 1975 and about 2 per cent over 1969. But black median income of $9,242 was slightly less than in both 1975 and 1969. (The median represents the mid-point of all incomes, and about 28 per cent of black famillies and 53 per cent of white families have income exceeding $15,000.)

A number of factors seem to explain the relatively unfavorable experience of blacks. In a slack economy, employers have a wider choice in hiring. Blacks may be losing more often in competition against more experienced and skilled workers. Or employers simply may be discriminating. Seriority ("Iast hird, first fired") probably hits blacks harder than white, and, most important, blacks - in central cities - simply don't live where job growth is fastest.

That particularly affects teenagers.

"If you go to a suburn Mc Donnalds, you're likely to see one adult surpervisor and all kids," said Robert Taggart, the director of youth programs for the Labor Department, "but if you go to a central- city McDonnald's> you're likely to find women and illegal aliens competing for those jobs." In the second quarter of this year, about 60 per cent of all unemployed blacks (845.000) lived in central cities.

One result of persisting high unemployment rates is a huge pool of discouraged workers: people who aren't looking for work and, in fact, may be searching for welfare. In 1876, about 8 out of 10 white men (aged 16 and over) were looking official labor force - that is, they either had a job or were looking for one - but only about 7 out of 10 blacks were.

Increasingly, male welfare among both blacks amd whites consists of disability payments. Between 1966 and 1972, the number of disability recipients increased by two-third, according to manpower econimists Taggart and Sar A. Levitan. in 1972, blacks accounted for 16 per cent of the severely disabled but only 9 per cent of the able-bodied adults, Levitan and Taggart content that low-income blacks, working in manual jobs are more likely to become disabled, with low incomes, more attached to benefits.

All this simply highlights the relative powerlessness of the White House to produced rapid economic gains for balcks. Even the illusion of gain may be difficult to achieve. Given the huge number of discouraged workers, any pickup in hiring is likely to lure more people back into the official labor force. Thus, the black unemployment rate may not decline sharply even when the number of jobs increases.

The administration is throwing money at the problem - creating temporary jobs and increasing government work training programs - but, more than in the 1960s, jobless whites compete for slots in these programs. More important, the temporoary nature of the programs means that unless the economy revives substantially, many of the beneficiaries simply will rejoin the umemployed when their participation expires.

What the Congresssional Black Caucus - and many liberals - want is something more permanent: the Humphrey-Hawkins bill, which would make the federal government the employerof last resort. But even if there were widespread public support for this costly solution, which there probably isn't, it involves huge risks. Making it easier for blacks to remain in depressed central cities might impede their movement to places where the number of better-paying jobs of rising fastest: the suburbs and the South and Southwest. In fact, that is one risk of the jobs component of the administration welfare program, which is sort of a mini-Humphrey-Hawkins bill.

In short, there is not good substitute for a genuine boom, but no boom is in sight. Carter may not want another war, but he probably wishes he had the economic equivalent.