We generalize the model of Krugman (J Polit Econ 99(3):483–499, 1991) to allow for asymmetric trade costs between regions and for (asymmetric) trade costs that are internal to the regions. We find that industrial activity, in a region, is enhanced by higher costs of importing and lower costs of exporting (more precisely, by a higher ratio between the two trade costs). This suggests that countries may impose tar...