The core periphery model with asymmetric inter-regional and intra-regional trade costs

We generalize the model of Krugman (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 tariffs on imported goods and seek to remove the import tariffs in other countries (unilateral protectionism) in order to foster industrial activity. Industrial activity is also promoted by lower domestic internal trade costs and higher foreign internal trade costs (more precisely, by a lower ratio between the two trade costs).