U.S. multinationals have and will continue to dodge over $100 billion in U.S. corporate taxes annually by registering their profits overseas, according to a study by Kimberly Clausing, an economics professor at Reed College. Lost U.S. tax revenue may reach as much as $135 billion in 2016—lopping off 23% of expected corporate tax revenue for the year.

Multinationals have argued that U.S. corporate income taxes, at about 35%, put them at a competitive disadvantage in relation to companies operating in lower tax areas. So they shift their profits abroad, usually by acquiring a company in a country with lower rates such as the Netherlands, Switzerland, or Ireland.

“The United States has one of the highest statutory corporate tax rates among peer nations, yet we raise comparatively little corporate tax revenue as a share of our gross domestic product,” the report noted. And if it continues at its current rate, tax revenue outflows will become a “large and increasing problem.”

Based on survey data from the Bureau of Economic Analysis, total U.S. tax revenue lost to profit shifting could reach $94 to $135 billion this year—up about 22% from four years earlier.

Aside from the attention tax inversion practices have received during the election cycle, federal officials have also sought to stymie the problem. A proposed $160 billion deal between pharmaceutical giants Pfizer and Allergan, which would have allowed the combined company to move to Ireland, broke down earlier this year.

The study suggests the U.S. government could do more to stop corporate inversions—including tightening the standards for a foreign affiliate to become a parent company.