Blacks moved into Washington's suburbs at such fast rate in the early 1970s that they accounted for nearly one sixth of the total increase in the number of blacks in the country's suburbs.

This conclusion is contained in a Ford Foundation financed study by demographers Eunice S. and George Frier for the Washington Center for Metropolitan Studies.

The center released the report yesterday, and it will be considered tomorrow by a fair housing panel at a conference here sponsored by the National Committee Against Diserimination in Housing and the Department of Housing and Urban Development.

The Grier study covers the years 1970 through 1974 and puts previously published figures on the black increase in the D.C. suburbs in a national context. Of the 668,00 increase in blacks in the nation's suburbs, 110,000 occurred in suburban Washington.

The total number of blacks in U.S. suburbs rose from 3.4 million to 4.1 million in those years, and the number in the D.C. area went from 179,328 in 1970 to 289,300 in 1974, from 8.3 per cent of the suburban population to 12.4 percent.

"The fact that the Washington are is getting about a sixth of the total black migration to the suburbs is sort of staggering," George said in an interview.

"It suggest the relatively little is going on elsewhere," he said. It's even more intersting when you consider that in 1970 the D.C. are had only 4.2 percent, or 717,000 people, of all blacks living in metropolitan areas - a total of 16.7 million."

The report attributed rapid movement of blacks to D.C.'s suburbs to three main factors: The black community here is relatively affluent; the federal government provides a stable income base and has encouraged a climate of equal opportunity, and the area has had "a vigorous citizen fair housing effort."

Grier said that if it had not been for the fair housing activity, "all the blacks would have ended up in Prince George's County."

The report said Prince George's continued to receive the major share of black suburban growth in the 1970s (68,400 of the 110,000 total) but that this was a smaller numerical percntage increase than in the previous decade - 62 percent in the early 1970s compared with 72 percent in the 1960s.

The Griens stressed that the figures do not tell how much of the suburban black population increase represents actual integration in housing.

But their report said that "the 42,000 person growth in the black population of other growth (besides Prince George's) was very widely dispersed

"Before the 1970s, blacks moving to suburbia had settled almost entirely in one locality - Prince George's." where." By the mid-1970s "there were few neighborhoods of any substantial size remaining in Washington's suburbs where there was not at least one black household."

The study noted that while "there were few new areas of black concentration . . one was clearly developing along the southeastern edge of Montgomery County adjoining pervious black concentration in D.C. and Prince George's." It also said "a good number" of blacks moving to Fairfax County went to Reston and to newer subdivisions.

In percentage terms the black movement to suburbs across the nation looks big, but in numerical terms it is still small, the report said. The 660,000 figure for the black increase compares with a 5.1 million increase of whites in suburbia.

However, the five-year black increase is large "when you consider that the number of blacks in suburbs grew only by 758,000 in the entire decade of the 1960s," George Grier said. The white increase in suburbs in the 1960s was 14.7 million!

In 1960 blacks constituted 4.8 percent of all suburban population. By 1970 the figure had dropped to 4.6 percent. But by 1974 it had risen to 5 percent, and in 1976 it was 5.3 percent, Griers aid. "This is important because it is a reversal of the previous declining trend," he added.

Across the country the number of blacks in the suburbs increased 19.5 percent in the early 1970s, compared with 7.3 percent for whites. In terms of suburban households, those occupied by blacks increased by 34 percent and those by whites 15 percent.

In the Washington area, black households in the suburbs increased by 39,400, or nearby 90 percent, and white households increased by 52,100, or 9 percent, in the early 1970s.

The Grier study shows that black households in the D.C. suburbs in 1974 made up 10.7 percent of the total, up from 6.5 percent in 1970.

Those figure compare with the following black household percentages in other suburban areas:

Atlanta - From 5 percent in 1970 to 6.6 percent in 1975.

Chicago - From 2.9 percent in 1970 to 3.7 percent in 1975.

Los Angeles - From 5.1 percent in 1970 to 7.1 percent in 1974.

Philadelphia - From 5.8 percnet in 1970 to 6.7 percent in 1974.

Detroit - From 3.2 percent in 1970 to 3.7 percent in 1974.

The Grier study also showed that the median income of suburban black families increased between 1970 and 1974, and so did that of central city whites. But among central city black families the median income fell by more than $400.

Suburban black families had a moedian income of $9,019 in 1974 compared with $8,388 in 1970. For central city blacks median income was $7,517 in 1974 compared with $7,953 in 1970.

"That reflects the fact that higher income blacks were moving to the suburbs," said Eunice Grier, "and those that were left in the cities included more of the elderly, single, and female-headed households.

In those years median income went from $13,593 to $14,214 for white suburban families, from $12,179 to $12,332 for white central city families, and from $10,469 to $12,961 for all families in metropolitan area (cities and suburbs).

"The income loss for central city blacks is even greater in relative terms because these figures are in constant dollars - not dollars weighted for inflation - and families needed a 24 percent increase in the four years just to stay even with inflation," said George Grier.