Matteo Manera, a Marcella Nicolini, b* and Ilaria Vignati c Futures price volatility in commodities markets: The role of short term vs long term speculation Abstract: This paper evaluates how different types of speculation affect the volatility of commodities’ futures prices. We adopt four indexes of speculation: Working’s T, the market share of non-commercial traders, the percentage of net long speculators over total open interest in future markets, which proxy for long term speculation, and scalping, which proxies for short term speculation. We consider four energy commodities (light sweet crude oil, heating oil, gasoline and natural gas) and six non-energy commodities (cocoa, coffee, corn, oats, soybean oil and soybeans) over the period 1986-2010, analyzed at weekly frequency. Using GARCH models we find that speculation is significantly related to volatility of returns: short term speculation has a positive and significant coefficient in the variance equation, while long term speculation generally has a negative sign. The robustness exercise shows that: i) scalping is positive and significant also at higher and lower data frequencies; ii) results remain unchanged through different model specifications (GARCH-in-mean, EGARCH, and TARCH); iii) results are robust to different specifications of the mean equation. JEL Codes: C32; G13; Q11; Q43. Keywords: Commodities futures markets; Speculation; Scalping; Working’s T; Data frequency; GARCH models _______ a University of Milan-Bicocca, Milan, and Fondazione Eni Enrico Mattei, Milan. E-mail:
[email protected] b University of Pavia, Pavia, and Fondazione Eni Enrico Mattei, Milan. E-mail:
[email protected] c Fondazione Eni Enrico Mattei, Milan.