The president of the Minneapolis Fed, Narayana Kocherlakota, explained in a speech yesterday how deflation is possible but unlikely. Near the end of his talk he provided the setup: “I mentioned earlier that inflation has been near 1 percent recently. These data have led some observers to worry about the possibility of a multiyear period of falling prices—that is, persistent deflation. I don’t see this possibility as likely. It would require the FOMC to make the surprising mistake of ignoring the long run in its desire to fix the short run.”

He then went on to explain:

Here’s what I mean. It is conventional for central banks to attribute deflationary outcomes to temporary shortfalls in aggregate demand. Given that interpretation, central banks then respond to deflation by easing monetary policy in order to generate extra demand. Unfortunately, this conventional response leads to problems if followed for too long. The fed funds rate is roughly the sum of two components: the real, net-of-inflation, return on safe short-term investments and anticipated inflation. Monetary policy does affect the real return on safe investments over short periods of time. But over the long run, money is, as we economists like to say, neutral. This means that no matter what the inflation rate is and no matter what the FOMC does, the real return on safe short-term investments averages about 1-2 percent over the long run.

Long-run monetary neutrality is an uncontroversial, simple, but nonetheless profound proposition. In particular, it implies that if the FOMC maintains the fed funds rate at its current level of 0-25 basis points for too long, both anticipated and actual inflation have to become negative. Why? It’s simple arithmetic. Let’s say that the real rate of return on safe investments is 1 percent and we need to add an amount of anticipated inflation that will result in a fed funds rate of 0.25 percent. The only way to get that is to add a negative number—in this case, –0.75 percent.

To sum up, over the long run, a low fed funds rate must lead to consistent—but low—levels of deflation. The good news is that it is certainly possible to eliminate this eventuality through smart policy choices. Right now, the real safe return on short-term investments is negative because of various headwinds in the real economy. Again, using our simple arithmetic, this negative real return combined with the near-zero fed funds rate means that inflation must be positive. Eventually, the real economy will improve sufficiently that the real return to safe short-term investments will normalize at its more typical positive level. The FOMC has to be ready to increase its target rate soon thereafter.

That sounds easy—but it’s not. When real returns are normalized, inflationary expectations could well be negative, and there may still be a considerable amount of structural unemployment. If the FOMC hews too closely to conventional thinking, it might be inclined to keep its target rate low. That kind of reaction would simply re-enforce the deflationary expectations and lead to many years of deflation.

While this scenario is conceivable, I consider it to be a highly unlikely one…