Buried in the middle of Table 1 in our new paper, Growth still is good for the poor, is a remarkable statistic: in a sample of 118 countries the average change in the income share of the bottom quintile of the population during the 2000s was 0.004. This is a small change, but what is striking is that it is positive. A common concern these days is that the people in the bottom part of the income distribution are being left behind. But these data show that there is no global trend in that direction. Similarly for the income share of the bottom 40%, there is no trend across countries, either in the 2000s or in earlier decades.
The other striking finding in this study, written together with Tatjana Kleineberg of Yale and Aart Kraay of the World Bank, is that changes in income share of the poor are uncorrelated with growth. In general, the relationship between the growth of mean income and the growth of income of the bottom 20% (or bottom 40%) is one-to-one; hence the title. Furthermore, about three-fourths of the variation in income of the poor across countries and over time can be accounted for by growth of average income. There are some interesting exceptions to the one-to-one relationship: Latin America in the 2000s had pro-poor growth with income of the poor rising significantly faster than mean income, while Asia had the opposite, pro-rich growth. We try to explain the changes in income share of the poor with a large number of variables covering dimensions of globalization, macroeconomic policy, and social policy (for example, government expenditure on health and education, primary school enrollment, or Gini coefficient on educational attainment). This part of the paper leads to a non-result: there are no robust correlates with changes in income shares.
What are the policy implications? I see both good news and bad news here. The fact that there is no worldwide trend towards lower income shares for the poor is good news. If there were such a trend it would suggest that globalization or some other general force was biased against the poor, and it would be hard to resist such a trend. But that is not the case. The rising inequality that we see in the U.S., for example, is not a general trend in rich countries. Other countries have found ways to maintain or increase the income share of the poor. It is also good news that growth will tend to raise the income of the poor proportionately, as it should always be possible to get most of the population to support a growth agenda. On the other hand, to the extent that we care about poverty reduction, it is bad news that we cannot explain what leads to changes in income shares of the poor and in particular what might bring about pro-poor growth.
Our findings do not imply that interventions aimed directly at the poor are pointless. But given the key role of growth in poverty reduction I favor interventions that build up the assets of the poor and enable them to participate in the market economy. A good example would be programs to ensure that the poor have access to maternal and child health services and early childhood education. Intuitively, you may think that such programs should shift income distribution in favor of the poor, and perhaps in some cases they do. But it also possible that the programs have powerful spillover benefits for the whole economy (more skilled labor, less crime – not to mention that the next potential Einstein will probably be born to a poor family in the developing world). If programs aimed at the poor have the side effect of stimulating the whole economy we should be happy about the higher growth, not disappointed that it is not pro-poor.