Wednesday, September 23, 2015

A Bad Optimization Problem

Roheeni Saxena writes

Economic inequality in the US has drawn attention to the attitudes and behaviors of the elite, as those who are educated in the top universities are both likely to start out wealthy and disproportionately likely to have an impact on the future of this country. To examine how this elite class would manage societal resources, the authors of a paper published in Science studied a group of Yale Law School students. 
The findings indicate that they’re more likely to make economic choices based on increasing the overall wealth of the nation rather than on increasing income equality within a nation. Thus, there’s a chance we’re selecting policymakers who are unlikely to address this issue.
Rather than anything nefarious, I think this phenomena is driven almost entirely by decisions being made using bad metrics, because good metrics are just too hard to calculate.

To make my point clearer, let $x = (x_1, ... , x_n)$ be a vector of variables quantifying the underlying real state of the economy. Maybe $x_1$ is nominal GDP, $x_2$ is inflation, $x_3$ is a 10 year yield, $x_4$ is unemployment, $x_5$ is some measure of consumption/income inequality, $x_6$ is average health outcomes, $x_7$ is average societal happiness, and so on.

The so-called elites in this study lean towards policy choices with an aggregate greater benefit to society, as measured in nominal dollars. So, for example, they may be trying to maximize the output variable $y = x_1$,  NGDP. Meanwhile, a more useful quantity to optimize might be $y = x_1 + c_2x_2 + \ldots + c_nx_n$, which incorporates all these factors with some weights $c_j$. This is much more complicated though, since you need a model which tells you how policy choices impact the full state $x$, along with variables $c_j$ quantifying how many units of $x_j$ are equal in net-beneift to a unit of $x_1$. Yikes.

Making good decisions requires good models. We don't have good models, so we make the best decisions we can, which are, of course, bad.

Monday, September 21, 2015

Williamson on Rate Hikes

He concludes

Central banks are not forced to adopt ZIRP, or NIRP (negative interest rate policy). ZIRP and NIRP are choices. And, after 20 years of Japanese experience with ZIRP, and/or familiarity with standard monetary models, we should not be surprised when ZIRP produces low inflation. We should also not be surprised that NIRP produces even lower inflation. Further, experience with QE should make us question whether large scale asset purchases, given ZIRP or NIRP, will produce higher inflation. The world's central bankers may eventually try all other possible options and be left with only two: (i) Embrace ZIRP, but recognize that this means a decrease in the inflation target - zero might be about right; (ii) Come to terms with the possibility that the Phillips curve will never re-assert itself, and there is no way to achieve a 2% inflation target other than having a nominal interest rate target well above zero, on average. To get there from here may require "tightening" in the face of low inflation.

So, given what we see, here are some possibilities:

1) Williamson and the Neo-Fisherites are right. It might hurt temporarily, but short term rates need to be raised if we want inflation to be higher in the long term.

2) Sumner, Svensson, Rowe, Friedman, etc are right. Inflation is purely monetary, and we aren't seeing it because we actually aren't doing nearly enough to budge the expectations on NGDP. Rates need to be kept 'low' (in fact, this crowd argues they're still 'high'). Moreover, if we want to do unconventional policies we need to not pay interest on reserves.

3) Neither group is right. Conventional monetary policy actually has no causal deterministic effect on inflation over some sufficient time horizon. Exogenous factors combined with psychological factors/expectations drive everything.

Addendum: Alan Derk adds the following

4) The economy is fundamentally changing (tech driven deflation or secular stagnation) and wrapping a macro model around it is missing the point.