If the Bank of Japan were a hedge fund, it would be congratulating itself on a blowout year, and getting ready to pay out enormous bonuses. When stocks plunged across the world in March and April as fears spread of a global COVID-19 depression, the BOJ waded into the Japanese market and bought exchange-traded funds, or ETFs, worth 2.7 trillion yen ($26 billion). A highly successful contrarian call, by the end of November, the Nikkei Stock Average had rallied 60% from its spring lows. Central banks are not usually noted for their market savvy.