International Capital Mobility in History: Purchasing-Power Parity in the Long Run

This paper investigates purchasing-power parity (PPP) since the late nineteenth century for a sample of twenty countries, a broader sample of pooled annual data than has been studied before. Econometric results for time-series and panel samples allows us to test the robustness of the PPP hypothesis in different eras: the gold-standard, interwar, Bretton Woods, and the recent float. The evidence for PPP is mixed: Strong PPP, entailing stationarity of the real exchange rate, is not broadly supported, and real-exchange-rate dispersion shows counterintuitive historical patterns. However, not-much-weaker forms of PPP can be supported, with evidence of cointegration between different countries' common-currency price levels. Residual variances here confirm the conventional wisdom that the interwar period, particularly the Great Depression, represented the nadir of international capital market integration in the modern era.