On the prevalence of trends in primary commodity prices

This paper applies new time series procedures to examine the Prebisch-Singer hypothesis of a secular deterioration in relative primary commodity prices. Specifically, we allow for (up to) two structural breaks in 24 price series, covering the 1900-98 period. For the majority of commodities, it is shown that the trend is not well represented by a single downward slope, but instead by a shifting trend that often changes sign over the sample period. Unlike some recent work that has also allowed for structural breaks, these results provide much less support for the Prebisch-Singer hypothesis.