As Fairfax County continues to grow, "there will be many more people able to pay taxes than there will be people requiring . . . services."

That optimistic prediction is one of the more significant conclusions in a recently published forecast on economic trends in Fairfax up to the year 2000.

The study, done for the county government by John Pershing Associates, says that as the county's population moves toward fewer children and more older people, the ratio of dependents to workers will continue to go down. As the ratio gets smaller, there will be more taxpayers but proportionately fewer people demanding services, the Pershing report says.

On the basis of this trend, the report says, "per capita expenditures and tax rates could decline except for inflationary effects."

The report does say that as the number of elderly people triples by the year 2000, there "may (be) more demand for programs for the elderly." But it also says that this demand "is expected to be more than offset by relative decline in demand for services to the young, particularly regarding schools."

But just how much remains problematical. Already the county is experiencing a drop in its school enrollment, but the costs of education have continued to rise, largely because the system, under state law, must devote more attention - which is to say, money - to special needs.

The Pershing report's projections on population and jobs in the country are not much different from some other recent studies, except that they are a little less bullish. The report says that Fairfax's population will grow from the present 567,500 to 949,800 by the year 2000 - a 61 per cent increase.

The report says that, by the year 2000, the number of jobs in the county could increase from the present 139,600 to 301,700 or 346,900, depending on how aggressively the local government courts industry and commerce.

The county has stepped up its economic development program in an effort to reverse a recent trend which has been homeowners assuming an increasing share of the real estate tax burden compared with business.

The report says that Fairfax should have a competitive edge on Montgomery County in attracting new business because the northern Virginia suburb has eight times the amount of available industrial zoned land inside or within 4.5 miles of the Capital Beltway.

Some other forecasts for the year 2000 in the Pershing report.

Development will have used up between 223,000 to 225,000 acres, or 80 per cent of the 257,000 acres in the county. In 1975, 163,000 (63 per cent) of the total acreage was developed.

The county, with only two major regional shopping centers, is "underserved with department stores" compared with suburban Maryland. A major new mall is planned at Tysons Corner, across the road from the present one, but rezoning has been delayed by a dispute between the developer and the county as to who should pay for elaborate road improvements. Rezoning, however, has been granted for a regional center at I-66 and U.S. Rte. 50 just west of Fairfax City.

While population will continue to grow at a slower rate than during the early '70s, new households will be formed at a higher rate. This disparity, the report says, "is the result of an increasing tendency for young adults and the elderly to maintain one-person households."