Inequality matters for growth and other macroeconomic outcomes, in all corners of the globe. One need look no further than the role inequality is thought to have played in creating the disaffection that underlies much of the recent unrest in the Middle East. And, taking a historical perspective, the increase in U.S. income inequality in recent decades is strikingly similar to the increase that occurred in the 1920s. In both cases there was a boom in the financial sector, poor people borrowed a lot, and a huge financial crisis ensued (see Leveraging Inequality, F&D, December 2010 and Inequality = Indebted in this issue of F&D). The recent global economic crisis, with its roots in U.S. financial markets, may have resulted, in part at least, from the increase in inequality. With inequality growing in the United States and other important economies, the relationship between inequality and growth takes on more significance. ...
Remarkably, inequality retains its statistical and economic significance even when we include many potential determinants at the same time, a claim that we cannot make for many of the conventional determinants of good growth performance, such as the quality of institutions and trade openness. Inequality still matters when we allow for regional differences in expected growth duration (such as between emerging Asia and Africa). This all suggests that inequality seems to matter in itself and is not just proxying for other factors. Inequality also preserves its significance more systematically across different samples and definitions of growth spells than the other variables do. Of course, inequality is not the only thing that matters but, from our analysis, it clearly belongs on the list of well-established growth factors such as the quality of political institutions or trade openness.