This article provides an overview of difference-in-differences estimation, starting with a review of the basic methodology, discussing in some detail recent advances in inference, and concluding with new methods for estimating treatment effects in various nonlinear and semiparametric models.

The paper examines the heterogeneity with respect to the impact of a financial reform - Activity Based Financing (ABF) - on hospital efficiency in Norway. Measures of technical efficiency and of cost-efficiency are considered. The data set is from a contiguous ten-year panel of 47 hospitals...

A framework for analyzing substitution and scale properties from plant-level panel data is presented. Focus is on comparing the constant and random coefficient specification of the substitution and scale parameters and investigating the variation of the parameters across plants. Characteristics...

Using panel data for Norwegian manufacturing, we revisit 'the increasing returns to scale puzzle' for labour inputs. We consider the response of the input of white-collar workers, blue-collar workers, and blue-collar worker hours to permanent changes in output. Permanent and temporary changes in...

Activity-based financing (ABF) was implemented in the Norwegian hospital sector from 1 July 1997. A fraction (30 to 50 per cent) of the block grant from the state to the county councils has been replaced by a matching grant depending upon the number and composition of hospital treatments. As a...

The impact of quality on the demand facing health care providers has important implications for the industrial organization of health care markets. In this paper we study the consumers' choice of general practitioner (GP) assuming they are unable to observe the true quality of GP services. A...

This paper deals with the (asymptotic) bias in the estimation of regression slope coefficients from panel data observed with error. Unobserved individual and time specific heterogeneity is also assumed. The estimators considered include: the standard "within" and "between" estimators, and...