The forward pricing function of industrial metal futures -- evidence from cointegration and smooth transition regression analysis

The prices of internationally traded metals have experienced wild swings and increased volatility in recent years. The relationship between spot and futures prices is an important topic in this context, as the current period's price of a futures contract should be an unbiased estimator of next period's spot price under the joint assumption of risk neutrality and rationality. Taking as a basis data from the Dow Jones UBS Commodity Index, which uses metals traded on the London Metal Exchange and US exchanges, this study adopts nonlinear smooth transition models to analyze whether the forward spread is a leading indicator of future spot price movements. Our findings suggest that such a price discovery function can in most cases only be identified in periods of low volatility or small previous spreads. Moreover, the underlying dynamics are captured best by the use of a logistic transition function.