Before revision:  Under mean-variance preferences, it is shown that each agent should share only a fraction of his true endowment and report that he is exposed to some endowment he does not possess. Furthermore, if all agents follow similar strategic behavior, the market equilibrates at a Nash-type equilibrium which benefits the speculators and results in risk sharing inefficiency. This agents ' strategic behavior, when applied to oligopoly markets of exogenously given financial securities, changes the effective market portfolio and implies a price pressure on the traded securities in the CAPM .
After revision:  Under mean-variance preferences, it is shown that at the (Nash) risk-sharing equilibrium, the sharing securities are suboptimal, since agents submit for sharing different risk exposures than their true endowments. On the other hand, the Nash equilibrium prices stay unaffected by the game only in the special case of agents with the same risk aversion. In addition, agents with sufficiently lower risk aversion act as predatory traders, since they absorb utility surplus from the high risk averse agents and reduce the efficiency of sharing. The main results of the paper also hold under the generalized models that allow the presence of noise traders and heterogeneity in agents' beliefs .