The renovation of inner-city neighborhoods, usually by young white professionals fixing up old homes, moved faster in Washington during the 1970s than in any other major American city, according to a new study by a Census Bureau demographer.

After two decades of substantial decline, the white population increased by 6.9 percent from 1970 to 1980 in the District's major renovation areas -- including Adams-Morgan, Mount Pleasant, Capitol Hill, and Shaw. At the same time, the number of blacks in those neighborhoods dropped by 36.3 percent, more than triple the rate of black population loss in the rest of the city.

Daphne Spain, the demographer who compiled the figures from the 1980 census, said Washington was the only one of 10 cities studied in detail to show a net gain of whites in its renovation areas. In all the others, Spain said, the exodus of working-class whites more than offset the influx of young professionals.

"Washington has all the right ingredients to be the leader" in renovation, Spain wrote in an article reporting her findings in American Demographics magazine. She said it has "a highly paid white-collar labor force; a large proportion of two-income households; an old and architecturally attractive housing stock, and such urban amenities as museums, theaters, and parks. These factors combine to set the stage for extensive renovation ."

While whites were moving into older neighborhoods close to downtown in the 1970s, their number dropped by 10.5 percent west of Rock Creek Park, the city's only large mostly white area. In the mostly black sections elsewhere, the remaining whites decreased by 36.2 percent.

Population shifts by blacks were sharply different, with a rapid increase of 25.8 percent west of Rock Creek Park -- though the number involved was still small -- and a relatively modest drop of 10.9 percent in other areas away from the city core.

Overall, the District's population declined by about 16 percent, to 637,651, during the decade, with blacks continuing to comprise just over 70 percent of all residents.

"There's been a lot of movement within the city even though the overall racial balance stayed the same," said George Grier, who is conducting a study of racial change in metropolitan areas for the Ford Foundation. "The impression that whites are 'taking over' the District is belied by the total figures. They are moving into a slice of the inner-city, but they're moving out of other areas."

Elsewhere around the country, Spain said, the extent of " 'gentrification' has been much exaggerated. There's been some conspicuous renovation near the core of almost every central city. It's made a psychological difference and a public relations difference, but so far the absolute number of newcomers hasn't been enough to offset the decline."

But Grier said that even though "Washington is ahead . . . a lot is going on in other cities, too. They're at an earlier stage. A lot of blacks and working-class whites are emptying out of inner-city neighborhoods. Young professionals are fixing things up and moving in. You just have to walk around to see it."

Virtually all of the areas near downtown Washington where black-to-white change is now occurring were built originally for middle-class or, in some cases, upper-income whites, according to a paper on "neighborhood resettlement" by Dennis E. Gale, an associate professor at George Washington University.

Most of Capitol Hill was built for those groups in the 19th century; it remained heavily white until World War II. Adams-Morgan and Mount Pleasant have large homes built for the wealthy around 1900 as well as stretches of middle-class row houses constructed in the first quarter of the 20th century.

Until about 1970, Gale said, most of those neighborhoods were going through a "filtering down" process as their older houses declined in physical condition and value, and families with lower incomes moved in.

This now appears to have turned around to a "filtering up" process, Gale writes. Childless "urban pioneers in their 20s and early 30s, usually with moderate incomes, buy dilapidated housing and start to fix it up. Then real estate investors and somewhat more affluent renovators move in, giving particular areas a more genteel identity that attracts the well-to-do."

Different neighborhoods are at different stages of this process, Gale said, which often moves gradually block-by-block.

For her study, Spain identified as a renovation area almost all of Capitol Hill south of H Street NE, north of the Southeast Freeway and west of 19th Street. The other major area runs from Dupont Circle east to North Capitol Street just above the downtown business district. Its northern limits follow Harvard Street, 16th Street NW, and Piney Branch Parkway.

During the 1970s, she found, the number of whites in those areas increased by 2,412, to 37,506, while the number of blacks dropped by 45,490, to 79,675.

The black decrease was almost 19 times greater than the white increase, reflecting a general depopulation of inner-city areas that has occurred in most other cities, too. Spain said two important factors involved were the drop in household size and the abandonment and destruction of rundown buildings.

Some deteriorated housing remains vacant for a considerable time before better-off newcomers move in, Spain said. Those who do come are usually one- or two-person households taking over space that had been occupied by large families.

No information is available yet from the 1980 census on where low-income blacks from the inner-city have moved. But Spain said it is likely that most now live farther out in the District in Northeast, Southeast, and upper Northwest, rather than the suburbs. Large numbers of middle-income black families who used to live in those city neighborhoods appear to have moved to suburbia, she said.

Grier said the renovation in most inner cities is "really a social class thing, not a race thing." Some blacks and interracial couples are among the renovators, he noted.

During the past year, he said, renovation may have been slowed by "high prices and high interest rates. But I think it's bound to continue."

Among the other cities studied by Spain, renovation was most widespread in Philadelphia, San Francisco and Seattle. Baltimore, she said, has had substantial renovation close to downtown but the revival has been counterbalanced by deterioration elsewhere.

The other five cities studied were Atlanta, Columbus, Ohio, Dallas, New Orleans and St. Paul. All were chosen because of reports of renovation -- which Spain concluded were exaggerated.