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Seis proposiciones nucleares del keynesianismo 

Twenty years ago, Tony Thirlwall (1993) summarised Post Keynesian macroeconomics in terms of six core propositions. First, employment and unemployment are determined in the product market, not the labour mar- ket. Second, involuntary unemployment exists, and is caused by deficient effective demand; it is not the result of labour market imperfections, and it would not be eliminated if such imperfections were removed. Third, the re- lationship between aggregate investment and aggregate saving is funda- mental to macroeconomic theory, and causation runs from investment to saving, and not vice versa. As James Meade (1975, p. 82) once put it, the “Keynesian Revolution” involved a mental shift, from the picture of a dog called “saving” that wags its tail called “investment”, to one of a dog called “investment” that wags its tail called “saving”. Fourth, a monetary economy is quite different from a barter economy: money is not neutral, finance is important and debt matters. Fifth, the Quantity Theory of Money is seri- ously misleading, for three reasons. Money is endogenous, so that in the Equation of Exchange (MV = PT) causation runs from right to left, not from left to right; changes in liquidity preference mean that V is not constant; and cost-push forces (especially pressures on wages and primary product prices) often generate inflation well before full employment is attained. Sixth, capitalist economies are driven by the “animal spirits” of investors, which determine investment. (This final proposition is somewhat problem- atic, as will be seen in section 8.3 below.)

The implications of Thirlwall’s six propositions are very clear, and ex- tremely important. Say’s Law is false, so that output and employment are often (perhaps normally) demand-constrained, not supply-constrained. Hence the maintenance of full employment often (perhaps normally) re- quires state intervention. Fiscal policy is not ineffective, and the principle of “Ricardian equivalence” is false (as Ricardo himself recognised). Finally, prices and incomes policies are needed to control inflation. In all of this, the bottom line is the principle of effective demand. 

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