Boston isn’t a cheap place to live, but a new report shows Massachusetts as a whole is severely undersupplied when it comes to housing stock for its low-income population.

The Bay State has less than half the needed apartments extremely low-income households can afford, and the Federal Reserve Bank of Boston expects the gap to widen in coming years without changes to affordable housing policy. The low-income category is defined as households earning no more than $29,150 for a family of three or $22,650 for a single person.

Massachusetts has 274,842 extremely low-income households, but there are only 128,037 apartments in the state with rents they can afford, the Boston Globe reports.

The low-income renter segment of the Massachusetts population has grown since 2011, but not as fast as higher-income segments. But the number of residential units low-income earners can afford without being rent-burdened (spending more than a third of their income on rent) has declined, and the situation is expected to get worse.

More than 9,000 subsidized residential units are expected to lose low-income subsidies in Massachusetts by 2025, which means 25 cities and towns across the state wouldn’t have any subsidized housing. Municipalities have looked to buy or refinance the units with expiring subsidies, but the Fed report forecasts it could cost between $843M and $1B annually to maintain and develop affordable housing in the state by 2035.

Affordable housing solutions have become an all-encompassing issue for Massachusetts developers and policymakers. Municipalities have set targets to build more housing supply to bring down prices, and Boston is weighing changes to its Inclusionary Development Policy that requires market-rate developers to create affordable residences in developments with 10 or mores units.

Some state politicians have also weighed enacting statewide rent control, but developers have warned such a measure would be a major headwind to the region’s ongoing building boom.