Many central banks reduced policy interest rates to zero during the global financial crisis to boost growth. Ten years later, interest rates remain low in most countries. While the global economy has been recovering, future downturns are inevitable. Severe recessions have historically required 3–6 percentage points cut in policy rates. If another crisis happens, few countries would have that kind of room for monetary policy to respond. To get around this problem, a recent IMF staff study shows how central banks can set up a system that would make deeply negative interest rates a feasible option. In a cashless world,...