The (Q,S,s) Pricing Rule
在Burdett和Judd的不完全竞争搜索模型中引入菜单成本，发现当菜单成本不太大时，卖家遵循(Q,S,s)定价规则，即让通胀侵蚀名义价格直至s点，然后支付菜单成本将名义价格重置为[S,Q]区间内的随机值。该均衡不同于标准(S,s)均衡，校准显示菜单成本只能解释名义价格持续时间的一半以下，且高通胀导致实际价格上升和福利下降。
We introduce menu costs in the search-theoretic model of imperfect competition of Burdett and Judd. When menu costs are not too large, the equilibrium is such that sellers follow a (Q, S, s) pricing rule. According to the rule, a seller lets inflation erode the real value of its nominal price until it reaches some point $s$. Then, the seller pays the menu cost and resets the real value of its nominal price to a point randomly drawn from a distribution with support $[S, Q]$, where $s<S<Q$. A (Q, S, s) equilibrium differs with respect to a standard (S, s) equilibrium: (1) in a (Q, S, s) equilibrium, sellers sometimes keep their nominal price constant to avoid paying the menu cost, other times because they are indifferent to changes in the real value of their price. An exploratory calibration reveals that menu costs account less than half of the observed duration of nominal prices. (2) in a (Q, S, s) equilibrium, higher inflation leads to higher real prices, as sellers pass onto buyers the cost of more frequent price adjustments, and to lower welfare.