More than 350,000 affordable housing units could vanish from the market during the next five years as housing built with the Low-Income Housing Tax Credit (LIHTC) over the past three decades begins to expire, according to an analysis by The Associated Press.

Launched in 1987, the federal LIHTC program provides tax credits to developers who promise to keep rents low. It is credited with helping bring 3.6 million affordable units to market nationwide. However, the terms of the tax credit usually only require the units to remain in the affordable category for 30 years. The LIHTC expirations come at a time when affordable housing is in high demand and inadequate supply, adding a layer of difficulty to what is already a crisis.

When affordability expires, rents can more than double, putting units out of reach financially for those who live there absent intervention. In some cases, tenants have banded together to force action from landlords and local officials when faced with evictions.