Small shoes and headroom

I talked with Kathleen Hays and Michael McKee on Bloomberg Radio last week, and they asked (twice!) a question that comes up often in thinking about Fed policy: shouldn't the Fed raise rates now, so it has some "headroom" to lower them again if another recession should strike?

I could only answer with my standard joke: That's like the theory that you should wear shoes two sizes too small because it feels so good to take them off at the end of the day.

But the question comes up so often, it's worth thinking about a little more seriously. Under what views about the economy does this common idea make any sense?

One way to think about the question: is the effect of interest rates on the economy path-dependent, so that a given level of short-term interest rates has more "stimulative" effect if it comes from a previously high value than if short-term interest rates were zero all along?

The usual answer is no. The model is usually a linear system, in which lowering the rate from a high value has the same effect as raising to the same rate coming from a low value.  In fact, the usual model goes the other way:  If, say, a new recession hits in June 2017 and you want more stimulus then,  having had rates at zero all along is more "stimulative" than having raised them to 3% between now and then, and lowering rates all of a sudden.  In equations, if \(y_t = \sum \theta_j i_{t-j} + \varepsilon_{t} \) with \(\theta_j \ge0 \) then the partial derivative of any \(y_t\) with respect to any \(i_{t-j}\) is the same no matter what the path of interest rates before time \( t-j\), and raising \( i_t \) today lowers future \( y_{t+j} \) given any set of shocks \(\{\varepsilon_t\}\)  You need some sort of nonlinear system where a higher interest rate today \(i_t\)  makes \( y_{t+j}\) more sensitive to some future rate  \(i_{t+k} \).

Another way to think about this question is to think about what sort of state variables the interest rate affects. If the Fed raises rates now, the economy will be in a different state in June 2017. So in what view of things does raising rates now put the economy in state such that the economy can better weather a shock, or, more to the point, a state in which lowering rates back to zero will be more "stimulative" than if rates were zero all along? People usually think that raising rates between now and May 2017 would lower inflation, output and employment over what they would have been otherwise. Then, once rates go to zero again in June 2017, inflation, output, and employment will be lower than if interest rates had been zero all along.

If the economy were to boom on its own, with inflation, output and employment rising, and the Fed were to follow that good news by raising rates, then yes the Fed would have more "headroom." But that's not an argument that the Fed can get the "headroom" by acting now.

In fact, the opposite  story has been told by those who advocate forward guidance and raising the inflation target. They argue that the Fed should keep rates lower and for longer, in order to raise inflation (the "state variable"). Higher inflation then indeed gives the Fed "headroom" to lower real rates by lowering nominal rates in the next recession.

What does it take to turn this around, and to justify the idea that raising rates gives "headroom" to lower them in the future? The main answer I can think of is to turn the conventional stories around. Suppose that raising interest rates raises inflation, as I have speculated before (here). The desired "headroom" is the desire to raise inflation, so that when June 2017 comes around the same nominal rate (0) corresponds to a lower real rate. I doubt many people articulating the policy view want to travel to Fisher-land and reverse the effect of interest rates on inflation.

You still need a second belief: that despite the wrong sign on inflation the conventional theory has the right sign on output: That lowering rates in June 2017 will fight that recession, even as it will lower inflation again. My little model didn't deliver that. Maybe other models do.

Loud disclaimer: I'm not advocating any position here. I'm just thinking out loud about what kind of views, if any, lie behind this common idea that raising rates now gives the Fed some sort of "headroom" to stimulate the economy in the event of a future recession.

This is a good case for real economic models. There is a lot of cause and effect chat surrounding monetary policy and financial policy that is way ahead of (if you're being polite) or outside of (if you're being accurate) any well-understood or even well-articulated economic model. By tying ideas together, perhaps a policy belief ("headroom") can open one's mind to an interesting causal channel (Fisher equation), or perhaps seeing that channel needed can reverse a policy belief.