Democrats’ New Tax Target Is $5 Trillion in Billionaire Wealth

With their latest tax proposal, Democrats are going after an elusive target: U.S. billionaires, and their growing piles of untaxed investment gains.

More than $5 trillion is held by Americans worth at least $1 billion, according to the Bloomberg Billionaires Index. This exclusive group -- more than 800 U.S. billionaires are now tracked by the index -- has more than doubled its collective net worth in the last five years.

Yet as the wealth of America’s billionaires soared, their tax bill didn’t rise by the same extent. Under the rules, investment returns are only taxed when assets are sold, ...