Accrding to new Keynesian view, if nominal imperfections are important to fluctuations in
aggregate activity, it must be that nominal frictions that are small at the microeconomic level
somehow have a large effect on the macroeconomy.Much of the research on the microeconomic
foundations of nominal rigidity is devoted to addressing the questions of whether this can plausibly
be the case.
　For concreteness, most of this section addresses this question for a specific view about the
nominal imperfection. In particular, we focus on a static model where firms face a menu cost of
price adjustment―a small fixed cost of changing a nominal price.