The results of a grudge match between Fairfax County and U.S. Census Bureau officials over population estimates for the county were released last week and the results were: feds -- 0, Fairfax County -- minus $2,000.

The $2,000 is the amount it cost county officials to conduct their own household survey rather than wait for results from the nationwide 1980 census.

The dispute began last fall when Fairfax officials challenged the census bureau's county population estimate for 1979. Fairfax contended the census bureau had underestimated the number of county residents by 39,900 -- possibly costing the county an undetermined amount of federal revenue sharing money.

Instead, according to the county survey, the county was off by 21,700 residents. The survey, conducted at random, shows that in 1979 Fairfax had 551,300 residents, well below the 573,000 estimated by the county. Based on those figures, the county now estimates that the population in January of this year was 600,300, down 2.2 percent from 1979 predictions.

Ironically, even if county officials had been proven right, there is no provision under federal revenue sharing guidelines to recoup the lost money.

"The county still had a principle here to prove," contends Fairfax County's director of research and statistics, David Sheatsley.

Sheatsley said that although the county conducts household surveys from time to time, the dispute with the federal government was the major reason for the recent survey.He said the county decided against waiting for federal census results because local information needed by the county probably would not be available for at least a year.