But the increase in receipts is misleading. During that period, for example, the top marginal tax rate went up, so the richest taxpayers were paying more. More important, in 2011, Americans had deep losses from the 2008 financial crisis that were still depressing tax obligations. In the following years, receipts outpaced economic growth, a typical phenomenon during recoveries. Still, that increase was weaker than government analysts expected. Even before last year’s tax cuts, tax receipts as a percentage of GDP never reached the levels of the late 1990s or mid-2000s.
It will be years before we know whether tax cheating has in fact increased. The last IRS report to assess what it calls the “tax gap,” issued in 2016, analyzed the period from 2008 to 2010. It found that taxpayers had paid about 82 percent of the taxes they truly owed. If the rate of compliance in 2017 was the same, that would translate to $667 billion in missing taxes.
Even the tiniest drop in compliance would cost billions more. But no one we spoke with who has worked at the IRS thinks the drop is likely to have been small. “One day it will be clear,” Koskinen said, “but by that time, you’re in deep yogurt.”