“In 2013, everything crumbled all at once,” Makera Meng said. She and her husband ran a business — an international grocery store — in South Portland, Maine, where they also owned a home. But that year, her mom died of cancer, they lost the business and her husband moved to Cambodia, where she had emigrated from three decades earlier. After 10 years of owning it, she lost her home, too. “I’m a good citizen, I work hard and I pay taxes,” she said. But she hasn’t been able to catch a break.

As a single mom raising four kids on little more than a welfare check, Meng qualifies for government housing assistance. But like most low-income Americans, she isn’t getting any. The waiting list for housing aid in South Portland is two to five years long; she’s been on it since 2013. In the meantime, she is paying $1,500 a month, utilities not included, for a three-bedroom apartment. “All the income I have is going to housing,” Meng said.

The Mengs are just one of millions of families across the U.S. that are struggling to find affordable housing. The government has established several housing assistance programs to help them, but the vast majority of poor Americans don’t receive any housing aid. And the problem is getting worse: The share of poor families that devote more than half of their income to housing costs has risen by 10 percentage points since 1991.

Activists and experts say the U.S. is in the midst of its worst affordable housing crisis in decades. “The evidence does suggest that since the 1960s, this is the worst it’s ever been,” said Barbara Sard, vice president for housing policy at the Center on Budget and Policy Priorities, a liberal think tank.

Experts say there are really two distinct problems. The first is affordability: Rents are rising, particularly in many expensive coastal cities, while wages for low-income workers have been nearly stagnant for much of the past 15 years. That leaves many poor families unable to afford housing on their own. Second, government housing-assistance programs haven’t kept up with demand even though new research suggests that unaffordable housing is an important cause of poverty.

The problem starts with affordability. For nearly 80 years — dating back to the Housing Act of 1937 — federal policymakers have defined families as being “burdened” if they spend more than 30 percent of their income on housing costs, including utilities.

But poor families often spend more than that. Just 20 percent of households earning less than $20,000 per year spent less than 30 percent of their income on housing, according to the 2013 American Housing Survey. Of the other 80 percent, about half devoted more than 50 percent of their income to housing. (For context: In 2013, the federal poverty guideline for a family of three was $19,530.) That’s a stark contrast to middle-class and affluent renting families, the majority of which paid less than 30 percent toward housing. And this trend has gotten worse: The percentage of renters below the poverty line who spent more than 50 percent of their income on housing rose from 42 percent to 52 percent between 1991 and 2013.

“Low-income people simply cannot afford low-income housing,” said Alex Schwartz, a professor of urban policy at The New School.

In theory, families that can’t afford housing can apply for one of several government assistance programs. The biggest one is the Housing Choice Voucher Program, also known as Section 8, which provides housing vouchers to about 2 million families, covering about 5 million people. Under the program, families rent homes on the private rental market; they pay up to 30 percent of their income to rent, and the voucher covers the rest, up to a local fair market rate.

Besides vouchers, the other major form of assistance is public housing, which is operated by local housing authorities. About 2 million people live in more than 1 million units nationwide. Public housing is more common in dense urban areas, where it’s often more cost-effective than vouchers.

But whether it’s vouchers or public housing, the vast majority of low-income families don’t receive any housing support. The programs are overwhelmed by the demand. Two-thirds of families at or below the poverty guideline receive no assistance at all, according to the 2013 American Housing Survey. About 17 percent get a government subsidy, 15 percent live in public housing, and 1 percent benefit from a rent-controlled unit.

HOUSING ASSISTANCE SHARE RECEIVING ASSISTANCE None 67% – Gov’t subsidy 17 – Public housing 15 – Rent control 1 – Two-thirds of poor families don’t get housing assistance Renter-occupied units at or below the federal poverty guideline in 2013 Sources: american housing survey, matthew desmond

For many of these families, the issue isn’t that they don’t qualify for help. It’s that the help they need isn’t available. That’s because unlike some other parts of the social safety net — such as food stamps — affordable housing is not an entitlement. Once the money appropriated by Congress runs out, the aid stops, no matter how much need there might be. According to the Center on Budget and Policy Priorities, 3 in 4 renting families that qualify for government housing programs don’t receive any assistance.

“Housing assistance is subject to funding availability,” said Schwartz, the New School professor. “And there’s the rub: The funding has not been available.”

For families that do get benefits, it usually comes after years on waiting lists, which are administered by thousands of local public housing authorities. The waiting lists are notoriously long. A survey conducted by an advocacy group in 2012 estimated that 2.8 million families were on waiting lists for housing vouchers. Andrew Aurand, the vice president for research for the National Low Income Housing Coalition, has recently conducted a survey of 320 representative public housing authorities. A full report on the results hasn’t yet been released, but the preliminary data is striking: Across all housing authorities, the median wait time for a voucher is 18 months; for public housing, it’s nine months. But even that understates the wait time for the average person because wait times tend to be longest at the biggest agencies. Among housing authorities that manage more than 5,000 units, the wait is three years for a voucher and two for public housing. In many large cities, the waiting list is so long that it’s closed.

Liberal housing activists argue that the main problem facing housing-assistance programs is lack of funding. Although funding got a boost from the stimulus package passed during the recession, it has since flatlined. Exacerbating trends in recent years is the so-called sequester that limited discretionary spending by the federal government. As of December 2015, for example, 45,000 fewer families were receiving Section 8 vouchers, which are administered by the Department of Housing and Urban Development, than were three years earlier.

Conservative critics, however, say the problem isn’t the lack of funding but the ineffectiveness of the programs themselves. Edward Pinto, a resident fellow at the conservative American Enterprise Institute, said existing housing programs cost far more than their headline budget amounts might suggest. Beyond the direct costs, he said, there are “layers” of subsidies to developers of rental housing through the tax code and federal financing agencies. “Not only are they very expensive, they aren’t even working,” Pinto said. “They create more problems than they solve.” A move to a less regulated and subsidized market would work better, he said.

What experts on both the left and right agree on is that the existing system isn’t working. Harvard sociologist Matthew Desmond, the author of “Evicted: Poverty and Profit in the American City,” a book on low-income renters in Milwaukee, said the U.S. effectively gave up on housing assistance after the very public failure of the public housing system in the 1970s and ’80s. When large-scale, government-constructed public housing projects such as Chicago’s Cabrini-Green became notorious slums, the government largely abandoned that approach without committing to a new one. “We just took the money away,” Desmond said. “It gave the impression that housing — that we tried and failed at this. We’ve never recovered from that.”

The government subsidizes housing to the tune of tens of billions of dollars each year. But most of that money goes to homeowners, not renters. Homeowners, for example, can deduct the interest they pay on their mortgages from their taxes; the deduction totaled about $70 billion in 2015, almost double the total budget of Section 8 programs, public housing and other housing tax credits for low-income people. A majority of the mortgage-interest deduction, in terms of dollars saved, goes to households earning at least $100,000.

Desmond said that by prioritizing assistance for homeownership — which mostly benefits middle-class and wealthy families — over rental assistance for the poor, the federal government is making the nation’s poverty problem worse. Because many poor renters don’t get assistance, and thus pay a large share of their income for housing, they’re at heightened risk of eviction. And eviction, Desmond finds, is far more common than previously realized. It’s a major cause of homelessness, and can easily lead to the loss of a job; more often than not, those evicted end up in housing of poorer quality. Children, in particular, suffer. Desmond argues that unaffordable housing, and the subsequent instability, is often the catalyst for a cycle of poverty. And in his book, he says that instead of focusing housing policy on increasing homeownership, we should be “pulling housing back to the center of the poverty debate.”

That would help Meng and her children. They feel settled in South Portland, Maine. “I can’t go anywhere; my kids love the school system,” she said. But when she lost her business and home and her husband left her, she thought housing assistance would be easy to get; she didn’t expect to encounter such a dysfunctional system.

When she first applied, Meng said she thought: “Well, I have nothing, but I’ll get situated in a couple months or a year.” Three years later, she still hasn’t gotten help: “It’s become a nightmare.”

Read more: How We Undercounted Evictions By Asking The Wrong Questions