This study gives an insight into the behaviour and performance of large speculators and large hedgers in 29 US futures markets. Using a trading determinant model and priced risk factors such as net positions and sentiment index, results suggest hedgers (speculators) exhibit significant positive feedback trading in 15 (7) markets. Information variables like the S&P500 index dividend yield, corporate yield spread and the three months treasury bill rate were mostly unimportant in large players’ trading decisions. Hedgers had better market timing abilities than speculators in judging the direction of the market in one month. The poor market timing abilities and poor significance of positive feedback results suggest higher trading frequency intervals for speculators. Hedging pressures, which measure the presence of risk premium in futures markets, were insignificant mostly in agricultural markets. As a robust test of hedging pressures, price pressure tests found risk premium to be still significant for silver, crude oil and live cattle. The positive feedback behaviour and negative market timing abilities suggest hedgers in heating oil and Japanese yen destabilize futures prices, and points to a need to check CFTC’s (Commodity Futures Trading Commission) position limits regulation in these markets. In fact, large hedgers in these two markets are more likely to be leading behaviour, in that they have more absolute net positions than speculators. Alternatively stated, positive feedback hedgers in these two markets are more likely to lead institutions and investors to buy (sell) overpriced (underpriced) contracts, eventually leading to divergence of prices away from fundamentals. / Atlhought hedgers in crude oil had significant positive feedback behaviour and negative market timing skills, they would not have much of a destabilizing effect over remaining players because the mean net positions of hedgers and speculators were not far apart. While the results are statistically significant, it is suggested these could be economically significant, in that there have been no regulation on position limits at all for hedgers compared to speculators who are imposed with strict limits from the CFTC. Further, mean equations were regressed against decomposed variables, to see how much of the futures returns are attributed to expected components of variables such as net positions, sentiment and information variables. While the expected components of variables are derived by ensuring there are enough ARMA (autoregressive and moving average) terms to make them statistically and economically reliable, the unexpected components of variables measure the residual on differences of the series from its mean. When decomposing net positions against returns, it was found expected net positions to be negatively related to hedgers’ returns in mostly agricultural markets. Speculators’ expected (unexpected) positions were less (more) significant in explaining actual returns, suggesting hedgers are more prone in setting an expected net position at the start of the trading month to determine actual returns rather than readjusting their net positions frequently all throughout the remaining days of the month. While it important to see how futures returns are determined by expected and unexpected values, it is also essential to see how volatility is affected as well. / In an attempt to cover three broad types of volatility measures, idiosyncratic volatility, GARCH based volatility (variance based), and PARCH based volatility (standard deviation) are used. Net positions of hedgers (expected and unexpected) tend to have less effect on idiosyncratic volatility than speculators that tended to add to volatility, reinforcing that hedgers trading activity hardly affect the volatility in their returns. This suggest they are better informed by having a better control over their risk (volatility) measures. The GARCH model showed more reliance of news of volatility from previous month in speculators’ volatility. Hedgers’ and speculators’ volatility had a tendency to decay over time except for hedgers’ volatility in Treasury bonds and coffee, and gold and S&P500 for speculators’ volatility. The PARCH model exhibited more negative components in explaining current volatility. Only in crude oil, heating oil and wheat (Chicago) were idiosyncratic volatility positively related to return, reinforcing the suggestion for stringent regulation in the heating oil market. Expected idiosyncratic volatility was lower (higher) for hedgers (speculators) as expected under portfolio theory. Markets where variance or standard deviation are smaller than those of speculators support the price insurance theory where hedging enables traders to insure against the risk of price fluctuations. Where variance or standard deviation of hedgers is greater than speculators, this suggest the motivation to use futures contracts not primarily to reduce risk, but by institutional characteristics of the futures exchanges like regulation ensuring liquidity. / Results were also supportive that there was higher fluctuations in currency and financial markets due to the higher number of contracts traded and players present. Further, the four models (GARCH normal, GARCH t, PARCH normal and PARCH t) showed returns were leptokurtic. The PARCH model, under normal distribution, produced the best forecast of one-month return in ten markets. Standard deviation and variance for both hedgers’ and speculators’ results were mixed, explained by a desire to reduce risk or other institutional characteristics like regulation ensuring liquidity. Moreover, idiosyncratic volatility failed to accurately forecast the risk (standard deviation or variance based) that provided a good forecast of one-month return. This supports not only the superiority of ARCH based models over models that assume equally weighted average of past squared residuals, but also the presence of time varying volatility in futures prices time series. The last section of the study involved a stability and events analysis, using recursive estimation methods. The trading determinant model, mean equation model , return and risk model, trading activity model and volatility models were all found to be stable following the effect of major global economic events of the 1990s. Models with risk being proxied as standard deviation showed more structural breaks than where variance was used. Overall, major macroeconomic events didn’t have any significant effect upon the large hedgers’ and speculators’ behaviour and performance over the last decade.

Cette thèse étudie le rôle joué par les investisseurs financiers sur les marchés des matières premières, connu sous le nom de financiarisation des matières premières. Elle est constituée d’une partie théorique et d’une autre empirique. Les recherches menées visent à étudier la participation des investisseurs, détenant des portefeuilles d’actions, aux marchés à terme de matières premières, pour des raisons de diversification. De plus, cette diversification peut être obtenue en investissant dans un panier de produits de base. Le premier chapitre analyse théoriquement l’interaction entre le marché des matières premières et celui des actions. Le deuxième chapitre étudie empiriquement l’impact du choix des investisseurs financiers sur la prime de risque des contrats à terme sur les matières premières. Il s’intéresse principalement à trois produits de base : pétrole brut (WTI), fioul pour chauffage et gaz naturel. Le troisième chapitre étudie théoriquement l’intégration de deux marchés de matières premières. Nous clarifions certaines considérations concernant l’effet de la financiarisation sur lesquelles la littérature existante reste hésitante. Nous démontrons le pouvoir d’influence qu’exercent les investisseurs sur le marché des matières premières. Toutefois, ceci dépend de la nature de la position de l’investisseur sur le marché à terme. De manière générale, la financiarisation entraîne la hausse des prix spot, des prix des contrats à terme et des niveaux des stocks. Nous montrons aussi que les investisseurs représentent un canal de transmission entre les marchés de matières premières. Leurs effets étendus se limitent à la corrélation croisée des marchés de matières premières. Enfin, nous montrons que les rendements des marchés d’actions sont devenus un déterminant de la prime de risque des contrats à terme après la crise financière de 2008. Cet effet des rendements des actions est indifférent entre les maturités courtes et longues. / This dissertation studies the role of financial investors on commodity markets, which is referred as financialization of commodity. The content of the dissertation splits to theoretical and empirical work. The implemented researches are motivated by the participation of investors, who own stock portfolios, in commodity futures markets for diversification reasons. Furthermore, that diversification is likely achieved by investing in a basket of commodities. The first chapter investigates, theoretically, the interaction between commodity and stock markets. The second chapter studies, empirically, the impact of financial investors on the commodities futures risk premium. It focuses on studying three commodities: crude oil (WTI), heating oil and natural gas. The third chapter examines, theoretically, the integration between two commodity markets. We clarify the hesitating of the previous literature in finding evidences of the impact of financialization. We confirm the influential power of investment in commodity market. However, that depends on the financial investors positions taken in the futures market. Generally, financialization increases the spot prices, the futures prices and inventory levels. We find, also, that investors are a transmission channel between commodity markets. Their effects spread out restricted to the cross commodity markets correlation. Finally, stock market returns became effective determinant of the futures risk premium after 2008 financial crisis. Also, the effect of the stock returns indifferent between short and long maturities.