Figure 4

Fit of experimental data on bilateral trade relationships with our theoretical law.

Note: We select the three largest provinces out of the available N_p and for each of them we consider the data for trade relationships Y_p,f performed between the province p and the foreign country f. The data for trade relationships Y_p,f are then analysed versus the fraction of migrants Γ_p,f residing in p and hailing from f and we perform the best fits according to the theoretical law in equation (17). Here we show the comparison between the empirical data (symbols) and best fits (solid lines) for Madrid (left panels), Barcelona (middle panels), Valencia (left panels). Different countries are depicted in different colours and symbols as specified by the legend. The foreign countries considered are those where Γ spans over the largest interval in such a way that fits can be more accurate.