An economist's foray into econophysics

I have described here some of the outlandish forays of physicists into Economics, where they try to use concepts from their discipline with disastrous results (last post here). But economists themselves may borrow concepts from physics. One that stuck was sunspots, from some chance correlation between sunspot activity and stock market performance, and made popular by David Cass and Karl Shell. But there were very little physics in this.

Martin Evans ventures deeper, using the concept of dark matter to understand exchange rate movements. It is well known that it is very difficult to understand what moves exchange rates. Dark matter is something that we cannot observe, but we see its impact. In this case, Evans builds a model where dark matter has an impact on nominal exchange rates, and then on other variables. This is based on the empirical observation that something like dark matter has an impact on expectations on long-run exchange rates, but not on recent and future interest rate differentials. This is achieved in the model by introducing shocks to household risk aversion. Why? Well, it is dark matter (or animal spirits). But all that matters is that it explains a large share of exchange rate fluctuations, in a rather consistent way for the other variables. Physicists would be happy with that. Economists would want to understand why.