Dynamic structure of the spot price of crude oil: does time aggregation matter?

- Strong evidence of general nonlinear serial dependence in daily spot price oil
- Evidence of nonlinear dependence is less dramatic in monthly observations.
- However, nonlinear dependence is still evident in oil price monthly data.
- The findings of nonlinearity are only slightly compromised by time aggregation.

This paper assesses nonlinear structures in the time series data generating mechanism of crude oil prices. We apply well-known univariate tests for nonlinearity, with distinct power functions over alternatives, but with different null hypotheses reflecting the existence of different concepts of linearity and nonlinearity in the time series literature. We utilize daily data on crude oil spot price for over 26 years, as well as monthly data on crude oil spot price for 41 years. Investigating the monthly price of crude oil along with the daily price distinguishes the approach of this paper from existing studies focusing on the time series structure of crude oil price. All the tests detect strong evidence of general nonlinear serial dependence, as well as nonlinearity in the mean, variance, and skewness functions in the daily spot price of crude oil. Since evidence of nonlinear dependence is less dramatic in monthly observations, nonlinear serial dependence is moderated by time aggregation in crude oil prices but not significantly.