Fig. 1
Annual trends of population and marriage indicators from the data set. In a we show the temporal evolution of the number of resident immigrants and of the total Italian population (time frame 2002–2010). As can be seen by direct inspection, the immigration is increasing during the years with a rate higher than the total population growth (see also the table in c). Since the municipality area is constant in this time window, we do not show the population density as it is simply obtainable via a rescaling by the total area and thus it has the same monotonicity as the latters. In b, we show the same temporal evolution for marriages: note that mixed and total marriages have opposite monotonicity. In c we summarize the variations of the observables considered along the time window analyzed. Finally, in d we show a scatter plot for mmix vs. Γ
