Three MMT Fallacies

I see three statements repeated by Modern Monetary Theory proponents, almost like mantras:

1. Money is endogenous
2. Banks don’t loan out reserves
3. There is no money multiplier

All three of these statements are either false, misleading, or meaningless, depending on how you define terms.

1. Endogeneity: Everyone has their reasons

When economists say a variable is endogenous, they mean it is explained by other variables in the model. Endogeneity is not an intrinsic characteristic of a variable, in the way that an apple is red or water contains hydrogen and oxygen atoms. Rather we find it convenient to regard variables as endogenous for the purposes of a certain analysis. Thus one should never say, “You’re wrong; money is endogenous”, rather you might want to claim that, “For the purpose of your analysis, it is more useful to regard money as endogenous.”

Monetarists often view the monetary base as being determined exogenously by the central bank, that is, at the bank’s discretion. At the same time, they understand that if the central bank is pegging some other variable, say exchange rates or interest rates, then the central bank has no discretion to adjust the money supply independently. They might still believe that changes in the money supply under that regime are very impactful, but there is no policy discretion for the quantity of base money.  Base money is endogenous.

Keynesians often regard the monetary base as being endogenous during a period of interest rate targeting, although with the advent of IOER the central bank can target the base and the interest rate independently. In Singapore, the central bank targets the exchange rate, and regards both interest rates and the monetary base as endogenous.

Things change if the central bank stops pegging interest rates at a constant level and instead targets them at a level that is frequently changed. While in that case the base can still be viewed as endogenous for the period when rates are fixed, it’s equally accurate to argue that the central bank adjusts its target interest rate in such a way as to allow desired changes in the base. Thus a central bank intending to do an expansionary monetary policy might cut the interest rate target in order to increase the monetary base. In that sense, they still do have some control over the money supply.  The money supply can be viewed as exogenous over a period of months.

All of this nuance is lost in MMT descriptions of monetary policy. Interest rates are viewed as exogenous and the base as endogenous. Any alternative approach is viewed as unthinkable.

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