Massachusetts Sen. Elizabeth Warren is scrambling to figure out how she would pay for a Medicare for All proposal without raising taxes on the middle class. But even if she were to confiscate the wealth of all of the billionaires in the world, it wouldn't even pay for three average years of Vermont Sen. Bernie Sanders's plan to socialize health insurance that she supports.

The liberal Urban Institute has calculated that a plan along the lines of what Sanders and Warren are advocating would raise federal spending by $34 trillion over a decade. The study does not include a year-by-year breakdown, but the average annual cost over 10 years would thus be $3.4 trillion, or $10.2 trillion for three years.

Yet earlier this year, Forbes estimated that the 2,153 billionaires in the world have a collective net worth of $8.7 trillion. That means even if the government were to magically vacuum up all of their wealth without any economic distortion, it wouldn't even pay for a third of the cost of the plan in the coming decade.

Of course, if this were done, in the second decade, when the program's cost would be even higher, the government would be out of billionaires to tax.

The largest revenue raiser Warren has proposed during her campaign is a wealth tax, which she claims would raise $2.75 trillion, not enough to cover a year of the healthcare proposal. Either way, she has already pledged to use the wealth tax to pay for universal child care, universal pre-K, a K-12 plan, a plan to raise child care worker pay, free college, and canceling student loan debt.

Editor's note: This story has been corrected to note the number refers to all billionaires in the world, not just the U.S.