Measuring internal trade distances: a new method applied to estimate provincial border effects in Canada

In this paper we suggest an improved methodology for comparing the intensity of trade across and within national and provincial boundaries, Earlier efforts to assess border effects for provinces or for countries without internal trade statistics made fairly arbitrary assumptions about average distances for internal trade flows. We improve on earlier efforts by taking more complete account of the distribution of population within each province or country. Internal distance is estimated as a population-weighted average of intra-city and intercity distances as well as distances to and within rural areas. We find higher estimates of internal distances, and hence border effects, than found in previous studies.