Testing for the existence of downward trends in real commodity prices has been the focus of several studies since the Prebisch–Singer hypothesis was formulated back in 1950. In this article, we focus on annual and monthly series of various commodity categories and consider alternative price...

In financial time series, persistence or inertia is a feature usually observable in absolute returns, i.e., a proxy for volatility. Moreover, asset return series should be essentially unpredictable according to the efficiency market hypothesis (EMH) in its weak form. Surprisingly, recent...

We apply linear and non-linear Granger causality tests to four U.S. price indices and 31 commodity series, which expand a 54-year period (January 1957–December 2011). We find evidence of linear Granger causality mostly from individual commodities to price indices. The latter, however, seem to...