The long-run behavior of real primary commodity prices, especially whether these series are trend stationary or contain a unit root, has been a topic of major debate in applied economics. In this paper, I perform a meta-analysis and combine the evidence of 12 representative studies on the subject in order to reach a unified conclusion about the presence of unit roots in these prices. The studies use different testing procedures, but share the common null hypothesis of a difference stationary process. Also, they use the individual price indices from the Grilli and Yang data set that is arguably one the most popular sources of long-term data on commodity prices. The combined evidence against unit roots in real primary commodity prices is strong: out of 24 cases, the unit root is not rejected in at most four. This rate means that real primary commodity prices are mean reverting and thus, to some degree, forecastable.

实际初级商品价格的长期行为，尤其是这些系列是趋势平稳的还是包含单位根的，一直是应用经济学中的主要争论话题。在本文中，我进行了荟萃分析，并结合了有关该主题的 12 项代表性研究的证据，以得出关于这些价格中存在单位根的统一结论。这些研究使用不同的测试程序，但共享差异平稳过程的共同零假设。此外，他们使用来自 Grilli 和 Yang 数据集的单个价格指数，该数据集可以说是最受欢迎的商品价格长期数据来源之一。反对实际初级商品价格单位根的综合证据很强：在 24 个案例中，单位根在最多 4 个案例中没有被拒绝。