神戸 伸輔

消耗戦モデルは交渉のモデルとしてしばしば使われてきた。しかし，もともと生物の駆け引きの分析のために考え出されたモデルを人間の交渉の分析に当てはめるために，いくつかの強い仮定が置かれている。この小論は，これまでのモデルが現実の交渉をうまく近似しているかを吟味する。３つの大きな疑問を立て，さらにそれらを小さな疑問に分解し，疑問に一つずつ答える形で定式化の妥当性について検討する。

We study in what circumstance players alternate offers in bilateral bargaining. To examine this question, we suppose that players choose whether to take the initiative in each period. The player who tries to take the initiative is able to make an offer only when the other player does not. The probability that a player tries to take the initiative is referred to as the frequency of initiative taking. We assume that this is conditioned on mutually observable states and is, once chosen, unchangeable. When players make their frequency of initiative taking dependent on the identity of the latest proposer, the players alternate their offers (possibly with some stochastic delay). In contrast, when players always use the same frequency of initiative taking, or when players only distinguish odd-numbered from even-numbered periods for the frequency of initiative taking, both players constantly try to take the initiative. Consequently, an impasse arises.

We study how a principal uses her subjective evaluation of the agent's performance in an incentive contract. It is shown that the subjective evaluation can be used either 1) when there is no other information about the agent's performance and the principal is able to discard money, or 2) when the principal chooses between wage payment based on subjective evaluation by foregoing objective evaluation, and the one based only on the objective evaluation and when the subjective evaluation is sufficiently accurate. The principal pays a high fixed wage when her rating at the subjective evaluation is above a certain level. On the other hand, when it is below that level, she either pays a low fixed wage or obtains objective evaluation and pays based on its outcome.

We study two-person complete-information bargaining games in a non-cooperative setting. The alternating-offers model in Rubinstein (1982) is modified so that players negotiate each time about who will make the next proposal. Under this rule, there are multiple equilibria and there can be a prolonged delay. The multiplicity and the possibility of delay remain either when offers have to be made alternately (under Restriction A) or when the players cannot increase their demands over time (under Restriction N). Only when both of these restrictions are imposed does the immediate settlement predicted by Rubinstein's original model emerge as the unique equilibrium. JEL Classification Number: C78.

We study the effect of imperfect commitment in noncooperative two-person bargaining games. By establishing the reputation for being stubborn, a player sometimes commits to her initial demand, becoming unable to change her demands or to accept an inferior offer from her opponent. When the probability of being stubborn is small, the set of equilibria is shown to be small and agreement may be reached immediately despite the possibility of stubbornness. A player has greater bargaining power when she is more patient and/or is more likely to be stubborn. Journal of Economic Literature Classification Number: C78. (C) 1999 Academic Press.