Goodhart’s Law – in Good Times and in Bad

A large part of the success of central banks all around the world during what became known as the Great Moderation is often attributed to the successful anchoring of inflation expectations to the levels that central banks would like to see – generally defined as 2% in most of the industrialized world. In basic theory this is awesome: if the inflation rate, through some kind of phillips curve or any other structural relationship you prefer, is linked to the aggregate level of economic activity in a stable way, than a stable inflation rate also leads to a stable level of economic activity.

In comes Charles Goodhart, former member of the Bank of England’s Monetary Policy Committee, who stated something as profound as at the same time similar to the famous Lucas Critique: Goodhart’s Law. In it’s most common version it says that “when a measure becomes a target, it ceases to be a good measure”. In other words, once a central bank (or in theory indeed any institution with enough clout to consistently affect the economy) states that it will do whatever it needs to in order to keep a given indicator at a level it so desires, the market structure will be affected by this, expectations of market agents will adapt, and the target will be achieved, even if the central bank does not really even do much – it just has to credibly promise that it would.

First of all, and on a very deep level, this of course could be seen as qualifying the very success of central banks in “anchoring” inflation rates. Has inflation in the past two decades been so tame because central banks have become better, or simply because they somehow managed to credibly make everyone believe that they have become better? In the end, the answer doesn’t matter much – it is outcomes that we want, who cares about how we get there. However, while the upside to this stable inflation anchoring in good times is enormous, it seems to have come back to haunt us at a time when we most need our monetary authorities to act. Even though inflation both in the US as well as in the Eurozone is considerably below target, inflation expectations are awkwardly close to those targets over the near-term (e.g. here for the Eurozone). Given most central banks nowadays target the forecast, they might interpret this as signalling that there is no real big need to act, and thus not act in the first place. I personally find this to be one of the most compelling explanations as to why the ECB continues to fail to do its job. As Draghi stated, “inflation expectations are firmly anchored in line with price stability“. Exactly. That’s the problem.

The Fed is in a somewhat better position since it does not only target inflation but also full employment – even if inflation sticks to 2%, as long as unemployment is above target it will (or should) ease monetary policy. The ECB, on the other hand, focuses essentially solely on inflation, and at the moment there are great doubts as to whether inflation (particularly inflation expectations) are of any use at all as a signal for what it should be doing. This monthly bulletin by the ECB (dating back to 2011, .pdf), for example, states that “well anchored expectations have contributed to enhancing the effectiveness of monetary policy and will assist the ongoing economic recovery”. Sure, stable inflation expectations also prevent us from falling into outright deflation in a scneario were we assume the central bank to be asleep. Further, as Clarida states (.pdf), “inflation inertia is the enemy of reflation once deflation set in”. However, I would state that somewhat differently: inflation inertia (in the context of this post in terms of expectations) is the enemy of reflation – period. At the moment it mostly provides a convenient excuse for central banks to do less than they should. Currently, it would seem that those well-anchored inflation expectations are part of what’s preventing effective monetary policy in the first place.

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