Policy interest rates are near zero (and sometimes below it) in most advanced economies, and the monetary base (money created by central banks in the form of cash and liquid commercial-bank reserves) has soared – doubling, tripling, and, in the United States, quadrupling relative to the pre-crisis period. This has kept short- and long-term interest rates low (and even negative in some cases, such as Europe and Japan), reduced the volatility of bond markets, and lifted many asset prices (including equities, real estate, and fixed-income private- and public-sector bonds).