The poorest people in the U.S. face the most acute shortage of affordable homes. That’s partly because the majority of low-income housing financed in recent years has been for those earning at least 50% of an area’s median income. Now, some cities are seeing an uptick in vacancies in these units as their rents approach those of market-rate apartments. As a result, some people who qualify are opting for market-rate apartments with less income-verification requirements and a faster chance of approval. It’s creating a paradoxical situation where some affordable units sit empty because the poorest people still can’t afford to rent them. Experts say more federal funding for housing vouchers is needed to bridge this gap.