Common risk factors in the returns of shipping stocks
Wolfgang Drobetz, Dirk C. Schilling, Lars Tegtmeier
Maritime Policy and Management | 03/2010
The knowledge of risk factors that determine an industry's expected stock returns is important to assess whether this industry serves as a separate asset class. This study analyses the macroeconomic risk factors that drive expected stock returns in the shipping industry and its three sectors: container, tanker, and bulker shipping. Our sample consists of the monthly returns of 48 publicly-listed shipping companies over the period from January 1999 to December 2007. We use shipping stocks together with a set of country or other industry indices to estimate the macroeconomic risk profiles and the corresponding factor risk premiums. Using a Seemingly Unrelated Regressions (SUR) model to estimate factor sensitivities, we document that shipping stocks exhibit remarkably low stock market betas. We also provide evidence that a multidimensional definition of risk is necessary to capture the risk-return spectrum of shipping stocks. A one-factor model produces large pricing errors, and hence it must be rejected based on tests of the model's orthogonality conditions using the Generalized Method of Moments (GMM). In contrast, when the change in the trade-weighted value of the US$, the change in G-7 industrial production, and the change in the oil price are added as additional risk factors, the resulting multifactor model is able to explain the cross-section of expected stock returns. The risk-return profile of shipping stocks differs from country and other industry indices. However, the sensitivities to global systematic risk factors are similar across all three sectors of the shipping industry. Overall, our results suggest that shipping stocks have the potential to serve as a separate asset class. Our findings also have important implications for computing the cost of equity capital in the shipping industry.