First Trillionaire: Elon Musk's Fortune and the Policy That Let It Happen

Elon Musk became the first trillionaire last month when SpaceX went public, according to Forbes. The milestone caps a century-long acceleration: it took 100 years to go from the first millionaire to the first billionaire, and another 100 to reach the trillionaire mark.

The numbers behind the trend show how the capital class has pulled away. The number of American billionaires has nearly doubled in a decade. Musk's net worth is up tenfold after inflation. The average family's wealth has grown a more moderate 40 percent. That is not a product of compound interest alone. It is a product of policy choices that amplify market inequality.

The policy infrastructure includes preferential treatment of investment income, low corporate taxes, the carried-interest loophole, estate-tax exemptions that have risen from $675,000 in 2001 to $15 million today, and weak antitrust enforcement. The top individual income-tax rate is less than half what it was in the 1940s and 1950s. The corporate rate is 14 percentage points lower than it was from 1993 until 2017. The United States does less to reduce inequality now than it did 15 or 50 years ago, and less than nearly any other high-income nation.