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Thoughts on the savings glut hypothesis

The “global savings glut” thesis was coined by Ben Bernanke in 2005, and refers to the notion that downward pressure on US interest rates was predominantly caused by excess savings in foreign trading partners such as China. One way to view this debate is that it is commonly believed that a countries current account is driving the capital account (i.e. that the latter is the source of financing for the former). Bernanke essentially pointed out the possibility that the causal arrow is stronger in the opposite direction – that strong demand for US assets (i.e. a capital account surplus) was driving the current account deficit.

In their case for the global savings glut thesis, Henderson and Hummel (2008) acknowledge that US interest rates were below their natural rate, but claim that Greenspan’s policy was “tight”. Selgin (2008) responded by downplaying measures of the money supply in favour of the interaction of the money supply and the demand for money. His argument is that if the PY side of the equation of exchange is volatile than so must MV by definition.  Interestingly, The Economist considered this in 2005, using basic IS-LM analysis to demonstrate that an increase in global savings would be revealed as a downward shift in the IS curve, cutting interest rates and reducing output. By contrast a monetary expansion would primarily affect the LM curve, also reducing interest rates but also increasing output. They conclude, that the latter case “seems to fit the facts more comfortably.

This blog post is simply a few fragmented thoughts on the claims made by Hummel, Henderson, and also Justin Reitz. For simplicity I'll refer to their collective position as HHR.

The HHR argument is along the following lines: the Fed only directly controls the monetary base, and it does so to ensure a stable US domestic price level. Since dollars that are held overseas have little impact on the domestic price level we should exclude them. Hummel and Henderson argue that since the ratio of currency to reserves is determined endogenously by the preferences of banks, it is better to focus on the Fed’s control of reserves, and they point out that reserves have approximately been frozen.

They do suggest that in theory one should really focus on the domestically held monetary base, and Rietz proceeds along these lines. He argues that since the currency held overseas has no direct impact on the domestic price level this should not count as evidence against a loose Fed policy. Indeed when foreign holdings of currency is stripped out he shows that the monetary base expanded by merely 2% per year. This supports Hummel & Henderson.

HHR makes an intriguing claim – not only that the Fed has been pursuing a de facto free banking monetary policy (i.e. keeping the base essentially frozen and then allowing fractional reserve banks to expand and contract the money supply on top of that to respond to changes in the demand to hold money), but that this is the true cause of the Great Moderation. No wonder they are surprised that Selgin doesn’t want to take credit for it! Rather, the bit that Greenspan was directly responsible for resembled a Free Banking environment.

But of course the incentive system within the existing regime (e.g. deposit insurance etc) means that the demand for money does not reflect voluntary behavior. HHR would say “but that’s not the Fed’s fault! Blame congress” and I sympathise. But regardless of whose fault it is it is at best an approximate free banking environment, and no one has argued that by resembling a free banking regime on one margin (whilst other margins are non free banking) is an improvement. Again, this comes down to whether you treat the regime as fixed, or expect the central bank to try to use what powers they do have to compensate for problems with the regime.

HHR don’t argue that the Fed didn’t play a role in generating the crisis. They merely show that it wasn’t within their narrow remit to prevent it. In isolation, a Fed that tries to limit its sphere of influence and sticks to approximating a free banking policy is a good thing. But in a world were governments create even bigger errors – whether foreign (in terms of their currency manipulation) or domestic (in terms of their addiction to debt financing) – maybe we should hold central bankers to a higher standard.

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