The efficiency of the crude oil markets: Evidence from variance ratio tests

This study examines the random walk hypothesis for the crude oil markets, using daily data over the period 1982–2008. The weak-form efficient market hypothesis for two oil crude markets (UK Brent and US West Texas Intermediate) is tested with non-parametric variance ratio tests developed by Wright (2000) and Belaire-Franch and Contreras (2004) as well as the wild-bootstrap variance ratio tests suggested by Kim (2006). We find that the Brent crude oil market is weak-form efficiency while the WTI crude oil market seems to be inefficiency on the 1994–2008 sub-period, suggesting that the deregulation have not improved the efficiency on the WTI crude oil market in the sense of making returns less predictable.