pesaran and smith show that under slope heterogeneity gmm and simple least square dummy variable dynamic fixed effect estimates of the speed of convergence are usually affected by a downward heterogeneity bias accordingly arnold et al rather looked at an error correction ecm version of equation a using pooled mean group pmg estimators which allow the speed of convergence to the steady state differ across countries this is a realistic approach as both exogenous ie solow and endogenous ie uzawalucas growth models imply that the speed of convergence to the steady state differs across countries because of crosscountry heterogeneity in population growth technical change and progressiveness of the income tax moreover the approach permits to discriminate between growth theories by glancing at the estimated parameters in fact for plausible values of the parameters the solow model implies a much slower speed of convergence to the steady state than that implied by the lucas model the paper concludes that the estimated speed of convergence is compatible with endogenous growth theories as mentioned this empirical approach could not be taken in the case of present analysis due to the lack of time series variation in inequality data