“A group of progressive Nobel Prize-winning economists has joined the fray in California’s battle over what would be the first wealth tax in the U.S. if state voters approve the measure in November,” the Financial Times reports.“Six laureates including Joseph Stiglitz and Peter Diamond have penned an open letter backing the proposed one-time 5 percent levy on billionaires, saying it could kick-start a movement to introduce wealth taxes across America and the world.”