It Takes t* to Tango: Trading Coalitions with Fixed Prices.

In the Edgeworth non-tatonnement process, trade occurs if there exists some coalition of agents able to make a Pareto-improving trade among themselves at current prices. It is known that the coalition size required is bounded by the number of commodities and that, provided all agents always have strictly positive endowments, bilateral trade suffices. These results are generalized, but it is shown that, when some agents do not hold all commodities, the information requirements for coalition formation can be very severe. Coalition size is not the only problem; very detailed information on preferences may be needed. Copyright 1989 by The Review of Economic Studies Limited.