GDP and unemployment interregional variation by country. Source: Authors’ calculation for Russia; Che and Spilimbergo (2012) for remaining countriesa. a Che and Spilimbergo (2012) calculate the population-weighted sum of absolute gaps between regional GDP per capita and national average, thus adjusting for the fact that different countries have different numbers of subnational units. They also take into account the fact that data are not available for some regions; they calculate national averages as population-weighted averages using the available sub-national data.