Before revision:  Specifically, we provide a tractable characterisation of the region of parameter values that exhausts all the implications of the model and data (the sharp identified set ) , under various classes of nonparametric distributional assumptions on the unobserved terms.
After revision:  Specifically, we provide a tractable characterisation of the region of parameter values that exhausts all the implications of the model and data (the sharp identified set , under various classes of nonparametric distributional assumptions on the unobserved terms.