“…The second strand, originating from Esteban and Ray [24], focuses on the rise of separated income groups: polarization increases if the population groups are getting more homogeneous inside and more separate one to the other. These pioneering contributions have been followed by many others, such as Wang and Tsui [59], Gradin [38], Chakravarty and Majumder [15], D'Ambrosio [19], Zhang and Kanbur [64], Duclos et al [22], Anderson [4], Esteban et al [25], Massari et al [44], Chakravarty and D'Ambrosio [14], Lasso de la Vega et al [42], Yitzhaki [63], Pittau et al [51], Permanyer [47], Silber et al [55], Lasso de la Vega and Urrutia [41], Chakravarty and Majumder [16].…”