A Congressional Budget Office report commissioned by Sen. Bernie Sanders and published Wednesday found the amount of unpaid taxes from 2011 to 2013 averaged around $381 billion per year, a revenue shortfall the Vermont senator called an “absolute outrage” that is largely the result of big corporations and “wealthy tax cheats” dodging their obligations.

“The richest 1% is responsible for 70% of all unpaid taxes,” Sanders said in a statement late Wednesday, pointing to a separate study of the so-called “tax gap” published last November.

The CBO analysis found that massive Internal Revenue Service budget cuts and staff reductions over the past decade have resulted in a sharp decline in examination and enforcement of tax underpayment and avoidance.

“Enforcement activity for many high-income nonfilers has been reduced to a series of notices,” the report says. The CBO’s findings bolster reporting by ProPublica last year that found the IRS “now audits poor Americans at about the same rate as the top 1%” due in part to the high costs of examining the tax returns of the rich.

“The IRS examination rate for the largest corporations, those with $20 billion or more in assets, dropped by about half from 2010 to 2018,” Sanders’ office noted. “The wealthiest taxpayers, with more than $1 million in income, saw their audit rate cut by 63% during the same time period.”

If the federal government collected the hundreds of billions in unpaid taxes owed mostly by the richest Americans, Sanders pointed out, “we could fund tuition-free college for all, eliminate child hunger, ensure clean drinking water for every American household, build half a million affordable housing units, provide masks to all, produce the protective gear and medical supplies our health workers need to combat this pandemic, and fully fund the U.S. Postal Service.”