Before revision:  Results: The model is experimentally validated with data of  Italian regions, European countries and US, obtaining fitting parameters in good agreement with previous literature.
After revision:  Results: The model is experimentally validated with data of Italian regions, some European countries, and the US. MAIN OUTCOME MEASURES: the accuracy of the model results is measured through the mean absolute percentage error (MAPE) and Lewis criteria; fitting parameters are in good agreement with previous literature.