Barro (2000) suggests that the negative impact of inequality on growth depends on how wealthy a country is, although this relationship is not robust. Using the two-step Arellano and Bond estimator, he found that income inequality depresses economic growth and was able to corroborate the convergence hypothesis, according to which initially low income or output levels are correlated with higher growth rates. These authors detected six such clubs, with the factors that reduced the inequality of income distribution in the municipalities of Brazil having asymmetric effects.