  The recent literature often cites Fang and Wang (2015) for analyzing the
identification of time preferences in dynamic discrete choice under exclusion
restrictions (e.g. Yao et al., 2012; Lee, 2013; Ching et al., 2013; Norets and
Tang, 2014; Dub\'e et al., 2014; Gordon and Sun, 2015; Bajari et al., 2016;
Chan, 2017; Gayle et al., 2018). Fang and Wang's Proposition 2 claims generic
identification of a dynamic discrete choice model with hyperbolic discounting.
This claim uses a definition of "generic" that does not preclude the
possibility that a generically identified model is nowhere identified. To
illustrate this point, we provide two simple examples of models that are
generically identified in Fang and Wang's sense, but that are, respectively,
everywhere and nowhere identified. We conclude that Proposition 2 is void: It
has no implications for identification of the dynamic discrete choice model. We
show that its proof is incorrect and incomplete and suggest alternative
approaches to identification.
