Additional controls are income groups in 2000 as convergence terms, latitude, landlocked, rule of law, civil liberties, population size, trade openness, inflation, oil, natural resources, urbanisation rates, life expectancy, fertility, ethnic fractionalisation, religion, unemployment rates, gender gap in outcomes and regional dummy variables. The quintile regressions estimated the SIGI coefficient for the median, the top and bottom quartiles. For the sake of brevity, only the variables of interest are presented.