Tax policy, usually an underdiscussed subject, has become a heated issue in the race for 2020, with Democratic candidates offering proposals to redress some long-standing unfairness in the tax code. Elizabeth Warren has a bold proposal to levy a new wealth tax, and Bernie Sanders is calling to significantly hike the rate on inheritances.

But before any new taxes are imposed, we have to grapple with a problem plaguing our existing tax structure: A lot of people already avoid paying what they owe. That problem is worst at the top of the income scale, yet the IRS too often expends its precious resources going after the poor.

Our current president offers a particularly egregious example of what the rich can get away with. Over the course of his time in the business world, there were two consecutive years when Donald Trump was the biggest loser in the country, and in numerous other years he bled more money than “nearly any other individual American taxpayer,” according to a recent bombshell report in The New York Times. He lost more than $1 billion over a decade. He has defended himself by pointing out that by declaring such big losses, he was able to reduce his tax bill. In fact, from what we can gather, he may have avoided paying any federal income taxes at all in many years.

Though Trump’s defense puts a big dent in his boasts about his business acumen, it is legal to write off losses. Still, his claims should raise red flags. According to tax-law professor Lily Batchelder, “Claiming large tax losses is one of a handful of positions taxpayers must automatically disclose to the I.R.S. as potentially abusive tax shelters.” And the Times has unearthed other examples of Trump and his family dodging taxes through schemes and, in some instances, outright fraud during the 1990s. That included setting up sham corporations to funnel money from his parents to him and his siblings, undervaluing their real-estate holdings by hundreds of millions of dollars, and taking improper deductions. Fred and Mary Trump gave their children over $1 billion but paid just 5 percent of it in taxes, despite the tax on gifts and inheritances at the time standing at 55 percent.

There are plenty of other ways Donald Trump has wriggled out of tax obligations. Some may be legal, and some are likely not, but all are troubling examples of the ways the rich can avoid paying their fair share. In the early 1990s, he used a complicated maneuver to essentially disappear hundreds of millions of dollars on which he would have owed taxes—a move “so legally dubious his own lawyers advised him that the Internal Revenue Service would most likely declare it improper if he were audited,” the Times reported in 2016. He has aggressively fought to reduce what he owes to state and local governments by arguing that the on-paper value of his properties should be lowered, even claiming to tax authorities that his holdings were worth less than the value he assigned them in other legal documents.

It’s impossible, of course, to say whether he has illegally shirked his tax obligations and, if he has, by how much and for how long. That’s because unlike every other president since Richard Nixon, Trump has refused to publicly release his tax returns. Even as Congress has sought to get the Treasury Department to turn over these documents, as it is legally obligated to do, the Trump administration has refused.

If he has indeed improperly avoided paying the IRS what he owes, that makes Trump pretty typical for his cohort. The more income people have, the larger the share of it they are likely to have misreported to the IRS. This phenomenon is most acute for the richest 1 percent; those most likely to accurately report their taxes, on the other hand, are the lowest-income filers.

But the IRS has become toothless when it comes to cracking down on tax evasion among the wealthy, thanks to a series of steep budget cuts over the last decade. Its annual budget has fallen by $2 billion since 2010. Audits have subsequently fallen by 42 percent as staff and resources dwindled. And they have declined most precipitously for the rich: Audits of the top 1 percent fell from 8 percent in 2011 to 2.5 percent in 2017, while the amount the IRS recouped from millionaires dropped by more than $3 billion over the last eight years. And when the rich do get audited, it tends to be a far less thorough undertaking than it was before the agency’s budget was cut.

That’s not to say that the IRS is sitting on its hands, though. As it’s gone easier on the rich, the agency has kept its sights trained on the poor. While the audit rate for those making millions of dollars a year has fallen 52 to 70 percent, it has dropped by only about a third for people who receive the earned income tax credit. Audits of EITC recipients, who make less than $55,000 a year, accounted for a bigger share of audits in 2017 than in 2011. “As the IRS has dwindled in size and capability, audits of the poor have accounted for more of what it does,” report ProPublica’s Paul Kiel and Jesse Eisinger. That’s because congressional Republicans have pressured the IRS to keep cracking down on the program’s overpayments, even as they continue slashing the agency’s budget. (Research suggests that when EITC recipients misreport, the problem usually lies in the complexity of the law, leading to honest mistakes—not because poor people are trying to defraud the government.)

If there’s a tax-evasion problem, it festers at the top of our income scale, not at the bottom. And yet the rich are outplaying the cop on that beat. Trump likes to brag that not paying taxes makes him “smart.” We shouldn’t let wealthy people like him outsmart our government and get away with shirking what they owe.