Washington's fringe area grew twice as the national average in the first half of this decade, according to a study just released by the Metropolitan Washington Council of Governments (COG). And, despite a much-heralded back-to-the-city movement, the trend will continue in the opposite direction, predicts the study's author, Carol Richards.

Washington's metropolitan fringe is composed of 16 counties and cities bordering on the counties that surround the District. In Maryland, the fringe areas are Anne Arundel, Calvert, Charles, Frederick, Howard, St. Mary's and Washington counties. In Virginia they are Clark, Culpeper, Fauquier, Frederick, King George and Stafford counties plus the cities of Fredericksburg and Winchester. Also included is Jefferson County, W.Va.

Among the highlights of the report:

The urban fringe's population increased by 13 per cent over the first four years of the decade, compared with national average growth rates only 3.4 per cent for the suburbs. While containing only a quarters of the entire area's population, the outer counties have accounted for almost half its growth since 1970.

At the same time, 90 per cent of the new jobs were found in suburban Maryland and Virginia, giving rise to the conclusion that the outer fringe is becoming the suburb's bedroom.

Two-thirds of the home buyers who bought property in one of the district's rehabilitated neighborhoods either moved there from another part of the city or moved in from another part of the country. The study indicates only 18 per cent of the people actually moved back to the city from the suburbs.

The study, funded in part by the Department of Housing and Urban Development, is intended to facilitate regional planning and development. Its main concerns are populations growth trends, housing construction, job trends and commuting patterns.

Richards concludes that Washington "real" region has expanded beyond its defined political boundaries. Just as a generation ago District dwellers fled to the suburbs but continued to work downtown, people are now moving to the fringe counties and working in the suburbs.

Further relocation of jobs away from the District, she concludes, can only widen the gap between workers in the city and job opportunities for them, the cost of which (unemployment compensation or welfare) will have to be borne almost entirely by the central city.

New York, suffering the effects of a similar exodus, has recently announced a campaign to keep business from leaving the city. Richards adds there is "no visible policy to stem this outward movement in Washington."

The reasons for the migration toward the fringe are primarily economic rather than psyclogical, the study surmised. Single-family detached homes cost at least $5,000 to $10,000less than in the suburbs.It is still possible to buy one for $40,000. Tax rates are lower, although they will increase as the growing population demands more like sewers and schools.

Only an action of "major proportion," such as doubling gasoline prices or putting a blanket restriction on new housing would reverse this trend, in Richards' opinion.

During the years 1970 to 1974 the fringe in Maryland grew much faster than the Virginia fringe due to the proximity of Baltimore. In fact 82 per cent of the entire fringe population increase was in Maryland. Howard County and the city of Frederick accounted for about half that or 41 per cent. Stafford county and the city of Fredericksburg led Virginia's increase. All of these jurisdictions lie along major interstate highways.

Fringe area housing construction more than tripled during 1970-1974 over the previous four year period. The fringe took away a considerable part of the suburbs' growth. While 83 per cent of all housing was built in the suburbs from 1964 to 1969, by the early 1970s only 44 per cent was erected there.

Most of the new housing consists of single-family dwellings or townhouses. The new towns of Columbia and St. Charles are exceptions, providing a variety of housing as well as recreational facilities and units for the elederly.

Despite aggressive industrial recruiting campaign, new industry has been slow to follow the migration to the fringe areas. The greatest increase in employment has been in the service sector, which has gained 26 per cent. Most of the industries that do settle in the fringe come from other parts of the country rather than from the metropolitan Washington area.

The report notes that no commuting census has been made since 1970 when a 173 per cent jump over 1960 from the fringe to the suburbs was noted. When such a survey is conducted again, it is expected to show a strengthening of that trend, if not another dramatic rise. CAPTION: Map, THE GREATER WASHINGTON REGION, By [WORD ILLEGIBLE] - The Washington Post