What distinguishes this from other NIMBY stories is that residents of Jefferson Park already have a proven way to prevent plunging property values as their neighborhood evolves: Nearly 30 years ago, a program geared toward halting white flight began on the Northwest Side. Called the Northwest Home Equity Assurance Program, the effort guaranteed the value of homes in the neighborhood, using a pool of money created by a modest yearly tax applied to homeowners within the program's boundaries. Most homeowners now pay between $1.50 and $3 a year into the program. The premise: If residents flee and property values fall, the program would make up the shortfall between a home's appraised value and the price it sells for. Yet home values have been steadily rising; the fund hasn't made a payout since 1998.