Are crude oil spot and futures prices cointegrated? Not always!

In previous studies, the cointegration relationships between crude oil spot and futures prices are confirmed based on Johansen (1988) test and vector error correction model (VECM). These conventional methods assume that the process of long-run equilibrium adjustment is linear. This paper revisits this topic employing nonlinear threshold VECM to take into account the nonlinear dynamics of equilibrium adjustment. Our results show that crude oil spot and futures prices are cointegrated only when the price differentials are larger than the threshold value. Moreover, we use a multi-frequency analysis based on low-pass filtering with different cut-off frequencies. The main findings indicate that the relationships between spot and futures prices are different between in the short-term and in the long-term. In the short-term, futures price plays the major role in the formation of long-run equilibrium (error correction mechanism). In the long-term, both spot and futures prices contribute to the dynamics of long-run equilibrium.