The Review of Economics and Statistics
We employ a unique dataset and new time series techniques to re-examine the existence of trends in relative primary commodity prices. The dataset comprises 25 commodities and provides a new historical perspective, spanning the 17th to the 21st centuries. New tests for the trend function, robust to the order of integration of the series, are applied to the data. Results show that eleven price series present a significant and downward trend over all or some fraction of the sample period. In the very long run a secular, deteriorating trend is a relevant phenomena for a significant proportion of primary commodities.
The Prebisch-Singer Hypothesis: Four Centuries of Evidence David I. Harvey, Neil M. Kellard, Jakob B. Madsen, and Mark E. Wohar. The Review of Economics and Statistics 2010 92:2, 367-377