Are we talking about income equality or income growth?
How does income inequality affect growth? I'd say there's plenty of other more pertinent factors in play, like technology, work ethic, competing in a global economy.
Income growth (inflation adjusted of course).
Take a look at the countries that have periods with a gini index over 0.6 (or 60, some groups multiply the calculation by 100 to get whole numbers). None of them have good growth.
The US after 2000 has seen a dramatic rise in the Gini Index, growth has stalled.
You can see this same pattern in France, Germany, the UK, and Japan.
In periods where the index rises, growth slows both nationally (GDP) and individually (median income).
