If history is any guide, the hefty tax cut that the Prince William Board of County Supervisors plans for this year could be followed by a tax increase next year. Twice before in the sometimes sporadic, generally ignominious history of the county's tax rate, supervisors have approved a big reduction in an election year, only to raise it the following year.

The most notable example was in 1987, when supervisors sliced 12 cents off the rate, making it $1.30 per $100 of assessed value. In 1988, after being admonished by credit agencies and needing to pay for struggling services, they were forced to raise it to $1.38. One election cycle earlier, in 1983, supervisors lowered the rate 3 cents and then raised it 3 cents the next year.

This year, supervisors have already lowered the rate proposed by County Executive Craig S. Gerhart from $1.19 per $100 of assessed value to $1.16 -- 7 cents below the current rate. And some, echoing the sentiments of the county's anti-tax constituency, are suggesting that it should slip further.

Few predict the dire consequences that befell the county in the 1980s, no matter what rate is adopted. Backers of lowering the tax rate note that the county dropped it 7 cents last year with no ill effects. In fact, the county's rate has dipped from $1.36 in 2000 to at least $1.16. All the while, homeowners' bills -- and county allocations -- have risen because of skyrocketing assessments.

Still, some worry that lowering the tax rate will make it hard to pay for new schools, fire houses and other capital projects in the years to come.

"If the tax rate goes below $1.16, it raises the question of what's our policy, what's our goal," Gerhart said. At that point, "it's not just about the tax rate, it's about what kind of community we want to have."

"Anything below $1.16 will start to impact school construction and renovations as well as teacher salaries," said board Chairman Sean T. Connaughton (R-At Large). "We have made dramatic drops in our tax rate . . . by sticking to our plans. It becomes a real problem if we turn our backs to these successful plans simply because it's an election year."

Whatever tax rate the Board of County Supervisors adopts this year, it will be a milestone. Most notably, the rate will be low enough to likely keep Prince William from having the distinction of being the highest taxed county in the state, a title it has held for as long as officials can recall. The rate will also be the lowest in county history.

In 1980, when officials converted to the current taxing system, the rate was $1.40. It peaked at $1.42 for much of the 1980s before settling at $1.36 for the 1990s. Many neighboring counties, meanwhile, had rates closer to $1 per $100 of assessed value, while Fairfax County stood somewhere in between.

County officials said the type of development the county attracted in the late 1970s and 1980s -- low-income residential -- contributed to the high tax rate. "We had a lot of affordable housing," Gerhart said, with costs of services "typical of Northern Virginia costs, but revenues that were not Northern Virginia revenues."

Government decisions also played a key role in the high rate. County officials did not have long-term budget plans or priority services then, so they tended to fund a handful of programs one year and then flip to prioritizing other services the following year, said Gerhart, a county employee since 1983.

In the '90s, officials decided they would concentrate their resources on what they determined were core functions, such as schools, roads and economic development. That helped curb budget battles and brought a clearer, longer-term strategy to the budget. But it also left some, such as the Park Authority, searching for other funding sources. The authority began building what it hoped were money generating facilities, but those continue to struggle to break even.

Nevertheless, county officials said they are pleased with how the current plan has worked and caution against lowering the tax rate too far.

"The history has shown us that when the market drops, it drops like a rock, and that's why sticking to our plans is so critical," Connaughton said. "We have attempted to budget to the middle, and by doing so we can avoid these wild swings that have negatively impacted us in the past."