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BPEA Article

It’s Baaack: Japan’s Slump and the Return of the Liquidity Trap

Kathryn M. Dominguez, Kenneth S. Rogoff, and Paul R. Krugman


THE LIQUIDITY TRAP-that awkward condition in which monetary policy
loses its grip because the nominal interest rate is essentially zero, in
which the quantity of money becomes irrelevant because money and
bonds are essentially perfect substitutes-played a central role in the
early years of macroeconomics as a discipline. John Hicks, in introducing
both the IS-LM model and the liquidity trap, identified the
assumption that monetary policy is ineffective, rather than the assumed
downward inflexibility of prices, as the central difference between Mr.
Keynes and the classics. ' It has often been pointed out that the Alice in
Wonderland character of early Keynesianism-with its paradoxes of
thrift, widows' cruses, and so on-depended on the explicit or implicit
assumption of an accommodative monetary policy; it has less often
been pointed out that in the late 1930s and early 1940s it seemed quite
natural to assume that money was irrelevant at the margin. After all, at
the end of the 1930s interest rates were hard up against the zero constraint;
the average rate on U.S. Treasury bills during 1940 was 0.014



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