A quick reading of two recent reports projecting substantial job growth in metropolitan Washington through the end of the 20th century can be misleading. A more careful analysis of projections for the next 15 years seems to be in order.

The National Planning Association, a Washington economic research organization, estimates that half of all jobs to be created by the end of the century will be concentrated in 30 metropolitan statistical areas (MSAs). Although a majority of those new jobs are expected to be in Sun Belt states, some mid-Atlantic areas, including metropolitan Washington, will be among the top 30. The National Planning Association projects an increase of 546,600 new jobs for the Washington MSA by the year 2000.

An increase of that magnitude would put the area's total employment at 2.4 million in five years, which translates into a 1.42 percent annual increase.

In the meantime, projections by the D.C. Department of Employment Services show that the number of jobs in the Washington Standard Metropolitan Statistical Area (SMSA) will approach 2 million in 1990, indicating an average annual growth rate of 2.3 percent over a 10-year span. In other words, nearly 372,000 jobs will be added between 1980 and 1990.

Unquestionably, the raw numbers contained in those projections and the favorable comparison with the booming Sun Belt can be useful in spicing up economic-development marketing programs. It never hurts to have a few impressive numbers available to support boosterism.

Bragging rights are less significant, however, than public policy, career decisions, business plans and training programs that will be formulated over the next few years. What matters most, then, is how well decision makers utilize the employment projections, especially those from the DES.

In developing its projections for the Washington SMSA, the division of labor market and information research in the DES made several assumptions that seem plausible enough, although any number of variables could render one or more of the assumptions invalid before 1990. The DES notes, in fact, that information about future employment growth is "clouded by uncertainty." What's more, say economists and researchers in the agency, it's important to understand the "imprecise nature" of projections, so that more realistic policy decisions are made.

With that as a caveat, therefore, the DES notes that its industry projections for the Washington SMSA are based on several assumptions about economic conditions between 1980 and 1990. Projections of employment in industry segments should be more meaningful to private and public policy makers when weighed against the following assumptions that the DES made about economic conditions in the 1980s:

* The national economic institutional framework will not change radically.

* Current social, technological and scientific trends -- including values placed on work, education, income, and leisure -- will continue.

* No major event, such as widespread or long-lasting energy shortages or war, will significantly alter the industrial structure of the economy or change the rate of economic growth.

* Industrial staffing patterns will change slowly, owing to changes in wages, technological advancements, or other factors.

* The economy will approach full employment.

If those assumptions hold up, the outlook for laborers and blue-collar workers in general is not encouraging. Already the area's smallest occupational group, laborers should not expect to see much more than a 1 percent increase in the number of jobs available at the end of the decade if DES's industry projections are correct.

At the other end of the employment spectrum, meanwhile, one of every five new jobs will be in the expanding services sector, according to DES's projections. At the same time, professional and technical workers are expected to replace clerical workers as the area's largest occupational group.

That doesn't necessarily mean that we will see an explosion in the growth of high-technology jobs in the Washington SMSA, as some would have us believe. The largest number of new jobs to be added to the labor market by 1990 will be in "traditional skilled and semi-skilled white-collar occupations and not the more glamorous 'high-tech' jobs," according to DES.

Jobs for elementary school teachers and sales clerks will grow in greater numbers than those for general office clerks and registered nurses. The growth rates for teacher aides and computer operators will be faster than those for computer programmers.

Those are important revelations for executives responsible for business expansion plans, educators, and those who formulate public policy. The imprecise nature of projections, notwithstanding -- the forecast error on total projected employment for 1990 is plus or minus 2 percent -- these are guideposts that can hardly be ignored.

The payoff for the region's economy in the long run, is how that information gets cranked into the planning process.