Republicans in Congress could finally get their wish to make it harder for poor people to access food assistance.

“Today, at the direction of President Donald J. Trump, we are taking steps to restore integrity to SNAP,” USDA head Sonny Perdue said in an op-ed Thursday, “and move people toward self-sufficiency.”

SNAP, the Supplemental Nutrition Assistance Program colloquially referred to as food stamps, has been helping keep Americans from going hungry since the 1960s. Perdue’s announcement came on the same day the president signed into law the new farm bill, which didn’t include SNAP work requirements Republicans in Congress had been pushing for.

Perdue’s proposed USDA rule is a farm-bill workaround, and it takes aim at “able-bodied adults without dependents,” ages 18 to 49. This group can’t access food stamps for more than three months during a three-year period unless they’re working or registered in an education or training program.

But states can request to waive that time limit, including if their unemployment rate exceeds 10 percent, or if the rate is 20 percent above the national average in certain regions. Thirty-six states and territories currently have waivers for some adults without dependents. States can also bank exemptions for later use, a practice Perdue referred to as “stockpiling.”

The new rule would crack down on the ability of states to access waivers by restricting them to areas where the unemployment rate is greater than 7 percent. The waivers would also be good for only one year to end “this hoarding of exemptions,” Perdue said.

Right now, three-quarters of the people targeted by this rule are not working, according to Politico. That’s 2.8 million people, of which 755,000 would lose SNAP benefits over three years if this rule goes ahead.

Republican leaders like acting White House Chief of Staff Mick Mulvaney and House Speaker Paul Ryan have long accused welfare programs like food stamps of being ineffective, arguing that they discourage people from seeking jobs. “If you are on food stamps and you are able-bodied, we need you to go to work,” Mulvaney said at a White House briefing last year, referring to stricter employment requirements the administration wanted to add to SNAP.

But there’s little evidence that the program discourages people from working, or that work requirements will alleviate poverty. That’s why nutrition advocates say the new rule could make life tougher on the most vulnerable Americans.

As Sarah Reinhardt, a food systems and health analyst for the Food and Environment Program at the Union of Concerned Scientists, said in a statement: “The administration’s insistence on restricting access to food assistance, despite strong opposition from experts and ample evidence of the program’s effectiveness, is simply mean-spirited.”

SNAP doesn’t discourage people from working

Before we go any further, some background on SNAP. The program began as a pilot under President John F. Kennedy in 1961 as part of the war on poverty. Today, it’s the biggest and most important nutrition assistance program: About 45 million Americans living below the poverty line — nearly half of them children — rely on SNAP to purchase food.

Administered by the states, low-income people who meet the eligibility criteria get access to “Electronic Benefits Transfer” cards (which are essentially debit cards) with money that they can use to purchase food. The lower your income, the more benefit you get (up to a monthly maximum of $194 per month for individuals and $771 for a family of five).

When researchers have looked at SNAP’s effects on food insecurity (having too little or uncertain access to food), they’ve found consistently positive effects. In a 2012 paper, researchers found SNAP cut the prevalence of food insecurity by at least 13 percentage points. In another 2013 study, researchers found exactly the same reduction in food insecurity when they studied variation in state-level policies that affect access to SNAP. Other studies have found the same association between SNAP participation and a decreased risk of food insecurity, albeit by varying amounts.

Yet one oft-repeated Republican Party line is that benefits like SNAP discourage people from working. But according to the researchers who study SNAP, there’s no good evidence that it acts as a work disincentive.

In fact, as the Center on Budget and Policy Priorities points out, the majority of non-disabled, working-age households that start to get SNAP don’t actually stop working.

Craig Gundersen, a professor of agricultural and consumer economics at the University of Illinois who studies SNAP, explained why in the Washington Post:

What makes SNAP perfect is that the tax on each additional dollar of income is 24 cents. There’s not a disincentive to work, except insofar as all taxes are disincentives to work. And I don’t think that 24 percent is a high tax rate in this context. There’s also no cliff effect with respect to SNAP, because as your income increases, your benefits gradually go down.

There’s also little waste and fraud in the program. Some 95 percent of federal dollars spent on SNAP go directly to benefits. The USDA takes SNAP abuse very seriously, which is why the rate of SNAP fraud has declined dramatically over the years.

Work requirements aren’t an effective poverty reducer

House Agriculture Chair Michael Conaway (R-TX) praised the new USDA rule for “creating a roadmap for states to more effectively engage [able-bodied adults without dependents] in this booming economy,” AP reported.

But there’s also little evidence that work requirements for government aid lift people out of poverty, as Dylan Matthews has explained.

The government has actually done numerous experiments to test out work requirements for cash welfare, as part of the state-level reforms leading up to the 1996 welfare reform law that imposed work requirements across the board. And the effects were meager at best, according to the Center on Budget and Policy Priorities’ LaDonna Pavetti, who reviewed this literature last year. She found the premise of work requirements — the presumed existence of a large number of people on public assistance who should be working and aren’t, due to laziness or inertia or whatever — just isn’t true. In most studies, work requirements led to an increase in the share of recipients working in the first year or two. But only three experiments out of 13 still found significant positive results after five years, and two experiments found that work requirements reduced one’s odds of working five years later. In the long term, the policy didn’t seem to promote work much at all.

Whether the new rule goes anywhere remains to be seen. House Democrats warned the SNAP changes would face tough opposition in Congress, since they ignored stipulations in the bipartisan farm bill.