In this paper we survey some recent developments of nonparametric econometrics in the following areas: (i) Nonparametric estimation of regression models with mixed discrete and continuous data; (ii) Nonparametric models with nonstationary data; (iii) Nonparametric models with instrumental variables; (iv) Nonparametric estimation of conditional quantile functions. In each of the above areas we also point out some open research problems. Forthcoming in Advances in Econometrics * We thank the referees for their careful reading of the manuscript and for their helpful comments. We also thank the Econometric Seminar audiences at the University of Guelph, and the participants in the Advances in Econometrics conference for helpful comments on this paper.
Logistics theory suggests that transportation and inventory policies are jointly considered by managers because these costs have offsetting properties. For example, when inventory is ordered less frequently, total transportation costs are likely to be lower due to economies of scale; yet inventory carrying costs are likely to be higher. This research analyzes aggregate transportation and inventory costs in the United States from 1960 to 2013, finding that, in the US economy as a whole, inventory and transportation costs are in long-term equilibrium. Furthermore, inventory seems to be adjusted for changes in transportation costs; however, transportation costs are not adjusted for changes in inventory costs.
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