The Standalone and the Portfolio Risk of the Rogers Energy Commodity Index

Abstract

This paper tackles the rather recent weekly period from January 18, 2005 to February 28, 2018, encompassing 523 observations. The portfolio is constructed from the perspective either of a US investor or of a Lebanese one, since the US dollar foreign exchange rate was pegged during the above whole period. The portfolio consists of an investment in the US S & P 500 stock market index and in three Rogers international commodity indexes: agricultural, energy, and metals. The purpose of the paper is to estimate the diversification benefits of the energy commodity index. These benefits arise from the fall in the volatility of the investment portfolio when it is compared to an investment in the energy index only, or in the S & P 500 only. The procedure follows the seminal approach of Markowitz. The inputs of the model are the variance/covariance matrix, the average log returns, and the condition that all investment shares should sum up to 1. The outputs, obtained by matrix manipulation, are the optimal investment shares in the four assets, the volatilities of the optimal portfolios, the characteristics of the efficient frontier, the relation between portfolio shares and the expected, or required return, and finally, the predicted Capital Market Line (CML). The evidence shows that, by holding a portfolio composed of the above four assets, the volatilities are substantially reduced. Moreover, and since short sales are allowed in the model, all optimal investment shares in the energy commodity asset are negative, meaning that in the optimal portfolios the positions in the energy index are short positions. The paper points to the significantly high relative riskiness of the energy index, as a stand-alone asset, or as an aggressive and speculative investment on the CML, and to the substantial portfolio benefits of shorting this index.