Today, the Tax Foundation released an analysis of Senator Bernie Sanders’s tax plan. In many ways, Sanders’s plan is the most ambitious plan proposed by any of the 2016 presidential candidates. It would increase federal taxes by $13.6 trillion on a static basis – larger than the tax cuts proposed by any Republican candidate. It would double the size of the estate tax, overhaul how international income is taxed, and create a new tax on financial transactions.

But perhaps the most ambitious piece of the Sanders tax plan is his proposed changes to the tax treatment of capital gains. Almost every country in the developed world, including the United States, taxes capital gains at a lower rate than other income, to avoid a double tax on savings and investment. However, the Sanders tax plan would end the current treatment of capital gains, and tax them “the same as income from work.”

Currently, the U.S. taxes income from capital gains at a top rate of 23.8 percent. When state and local taxes on capital gains are included, this figure rises to 28 percent. Under the Sanders tax plan, the federal tax rate on capital gains would double, to 54.2 percent (or 58.4 percent, after including state and local taxes).

These changes would give the United States the highest tax rate on capital gains in the world, by far and away. Currently, the “leader” in capital gains taxes is Denmark, with a top rate of 42.0 percent on capital gains. Most countries in the OECD have top capital gains rates around 20 to 25 percent, while nine countries do not tax capital gains at all.

Under the Sanders plan, the United States tax rate on capital gains would be 16.4 points higher than Denmark’s. Such a high rate on capital gains would be historically unprecedented; since 1922, the U.S. tax rate on individual capital gains has never risen above 35 percent.

Even liberal policy commenters are skeptical of Senator Sanders’s proposed changes to the taxation of capital gains. Many cite a paper by David Kamin that suggests the revenue-maximizing rate on capital gains is between 28 and 32 percent. In other words, if Congress raised the tax rate on capital gains above the current level, individuals would realize their investments less frequently, and the federal government would actually start to lose revenue.