Near unit root and the relationship between inflation and interest rates: A reexamination of the Fisher effect

Tests of the Fisher effect are plagued by high persistence in interest rates. Instead of standard regression analysis and asymptotic results, methods relying on local-to-unity asymptotics are employed in testing for the Fisher effect with monthly U.S. data covering the period 1953:1–1990:12. These procedures are extensions of a recently presented method (Cavanagh, Elliott and Stock (1995)) based on simultaneous confidence intervals, and they have the advantage of being asymptotically valid whether interest rates are integrated of order one or zero, or near unit root processes. Taking appropriately account of the near unit root problem the findings in most of the previous literature are reconfirmed. There is support for the Fisher effect in the interest rate targeting period (1953:1–1979:10) of the Federal Reserve but not in the 1979:11–1990:12 period. First version received: July 1999/Final version received: April 2000     

Testing for weak-form efficiency of crude palm oil spot and future markets: new evidence from a GARCH unit root test with multiple structural breaks

There is a sizeable literature that tests for weak-form efficiency in commodity and energy spot and future prices. While many studies now allow for multiple structural breaks to address the criticism that conventional unit root tests have low power to reject the unit root null in the presence of structural change, the extant literature overlooks the fact that conventional unit root tests are biased in the presence of conditional heteroscedasticity. We apply a recently developed generalized autoregressive conditional heteroscedasticity (GARCH) unit root test with multiple structural breaks to crude palm oil spot and future prices and find much more evidence against weak-form efficiency than that found using tests that fail to allow for conditional heteroscedasticity. Our results point to the importance of allowing for heteroscedasticity when testing for efficiency in commodity and energy spot and future prices.