Commodity currency

Abstract: We show that “commodity currency” exchange rates have surprisingly robust power in predicting global commodity prices, both in-sample and out-of-sample, and against a variety of alternative benchmarks. This result is of particular interest to policy makers, given the lack of deep forward markets in many individual commodities, and broad aggregate commodity indices in particular. We also explore the reverse relationship (commodity prices forecasting exchange rates) but find it to be notably less robust. We offer a theoretical resolution, based on the fact that exchange rates are strongly forward-looking, whereas commodity price fluctuations are typically more sensitive to short-term demand imbalances.

Abstract: This paper is an econometric investigation of the determinants of the real value of the South African rand over the period 1984-2007. The results show a relatively good fit. As always with exchange rate equations, there is substantial weight on the lagged exchange rate, which can be attributed to a momentum component. Nevertheless, economic fundamentals are significant and important. This is especially true of an index of the real prices of South African mineral commodities, which even drives out real income as a significant determinant. An implication is that the 2003-2006 real appreciation of the rand can be attributed to the Dutch Disease. In other respects, the rand behaves like currencies of industrialised countries with well-developed financial markets. In particular, high South African interest rates raise international demand for the rand and lead to real appreciation, controlling also for a forward-looking measure of expected inflation and a measure of default risk or country risk.