Financial shares are down sharply in 2016 even as broader markets have recovered; central-bank policies squeeze interest margins --- Bank stocks are having a terrible 2016, as central-bank policies, which for years lifted asset prices, are hurting the financial sector. The impact of economic stimulus efforts on lenders will get a fresh airing this week, as big U.S. banks begin reporting their earnings for the first quarter. Trading revenue is expected to have taken a hit, but the more enduring problem will be visible in the lenders’ net interest margins, the basic measure of bank profitability that gets flattened by...