A major unsolved riddle facing the social sciences is the cause of impasse in negotiations. The consequences of impasse are evident in the amount of private and public resources spent on civil litigation, the costs of labor unrest, the psychic and pecuniary wounds of domestic strife, and in clashes among religious, ethnic and regional groups. Impasses in these settings are not only pernicious, but somewhat paradoxical since negotiations typically unfold over long periods of time, offering ample opportunities for interaction between the parties.Economists, and more specifically game theorists, typically attribute delays in settlement to incomplete information. Bargainers possess private information about factors such as their alternatives to negotiated agreements and costs to delay, causing them to be mutually uncertain about the other side's reservation value. Uncertainty produces impasse because bargainers use costly delays to signal to the other party information about their own reservation value (Kennan and Wilson, 1989; Cramton, 1992). However, this account of impasse is difficult to test because satisfactory measures of uncertainty are rare. With only a few exceptions (Tracy, 1986(Tracy, , 1987, most field research in this area has been limited to testing secondary hypotheses, such as the relationship between wages and strike duration (