The popular 'airline' model for a seasonal time series assumes that a variable needsdouble differencing, i.e. first and seasonal (or annual) differencing.The resultant time series can usually be described by a low order movingaverage model with estimated roots close to the unit circle. This...

In a number of semiparametric models, smoothing seems necessary in order to obtain estimates of the parametric component which are asymptotically normal and converge at parametric rate. However, smoothing can inflate the error in the normal approximation, so that refined approximations are of...

Our paper empirically investigates the structure of transport costs for interregional trade, by using the micro-data of freight charge. We focus on road transport, reflecting the fact that trucking has a dominant share in transporting goods between regions in many countries (in Japan, 91.2% of...

This paper presents an approach to measuring the values of time cost for freight transportation, and examines its applicability through empirical analysis. We develop the method based on the hedonic approach by explicitly formulating how transport time is determined as market outcome. In the...

In this paper, we propose a doubly robust method to present the heterogeneity of the average treatment effect with respect to observed covariates of interest. We consider a situation where a large number of covariates are needed for identifying the average treatment effect but the covariates of...

Our confidence set quantifies the statistical uncertainty from data-driven group assignments in grouped panel models. It covers the true group memberships jointly for all units with pre-specified probability and is constructed by inverting many simultaneous unit-specific one-sided tests for...