Wealth tax: Tax net worth over $50 million at 2% a year, and 6% above $1 billion. To prevent the rich from yachting off, add a 40% “exit tax” on assets over $50 million upon renouncing U.S. citizenship. Estimated revenue: $3.75 trillion over a decade from 75,000 households. Most economists, including many Democrats, call that number a fantasy. Courts might also find the tax unconstitutional.