Before revision:  Our tools show how to sharply characterize what we can learn when demand is allowed to remain entirely nonparametric or to be parameterized in a flexible manner, both of which imply that the parameters are not necessarily point identified.
After revision:  We show how to sharply characterize what we can learn when demand is allowed to remain entirely nonparametric or to be parameterized in a flexible manner, both of which imply that the parameters are not necessarily point identified.