The dependent variable GDP per capita, expressed in euro at county level, is considered as the best available
measure to account for the economic growth of the growth poles. Data was not readily available for the growth poles
themselves for a period long enough to generate a time series on which to do the analysis. However, given the
relative size of the economic activity located in the growth poles within the counties they belong to, and considering
their multiplier effects for the entire economy of the county, GDP per capita at county level was deemed as the best
dependent variable to be used.