A Remark on Conjectural Equilibria
证明猜想均衡与固定价格均衡在分配上等价，说明任意猜想下两者导致相同结果，对理解非市场出清下的价格刚性有参考价值。
The notion of a conjectural equilibrium was introduced by Hahn (1978). The underlying idea is to explain why prices may not change in a situation where markets do not clear and rationing occurs. In a conjectural equilibrium, prices are rigid because it is not in the interest of agents to change them. More precisely, agents conjecture prices at which they can achieve a trade beyond the given quantity constraints such that it is better for them to trade at the observed market prices within the constraints. Therefore, the question of whether an allocation for given prices and quantity constraints is a conjectural equilibrium depends crucially on the agents' conjectures in this situation. By allowing arbitrary conjectures, many such equilibria will exist, as has already been claimed by Hahn (1977 a, 1977b and 1978). In this note it is shown that there are as many conjectural equilibria as there exist fixed-price equilibria which satisfy the condition of voluntary exchange only. To be more specific, we prove that any conjectural equilibrium is a fixed-price equilibrium and that for a given economy, there are conjectures such that any fixed-price equilibrium is a conjectural equilibrium. In other words, the kind of endogenous price setting described in Hahn's model turns out to be equivalent to the fix-price approach in the sense that both lead to the same allocations in the economy. The result confirms the statement in Drazen (1980) that by allowing arbitrary conjectures only one exogenous variable (prices) has been replaced by another (conjectures).