GDP per capita, PPP - Country rankings

Definition: GDP per capita based on purchasing power parity (PPP). PPP GDP is gross domestic product converted to international dollars using purchasing power parity rates. An international dollar has the same purchasing power over GDP as the U.S. dollar has in the United States. GDP at purchaser's prices is the sum of gross value added by all resident producers in the economy plus any product taxes and minus any subsidies not included in the value of the products. It is calculated without making deductions for depreciation of fabricated assets or for depletion and degradation of natural resources. Data are in constant 2011 international dollars.

Is the world income inequality getting smaller?

If poor countries grow faster than rich countries, over time they will catch up in terms of their level of income measured by GDP per capita in PPP terms. This process is called income convergence. Alternatively, incomes would diverge if the rich countries grow more rapidly than poor countries. If economic growth is the same everywhere, then the differences in income across countries would remain the same. There are two main reasons for why incomes across countries might converge over time.

Technology spillover. One reason is that innovations and technologies that are developed in the rich countries soon become available in the poor countries. That happens, for example, through foreign direct investment as companies from the rich countries bring new technologies to the poor countries. When the same technology is available everywhere, then incomes would also tend to become equal over time because technology is an important ingredient of economic development.

Based on that argument, incomes would converge faster if a poor country is ready to use the advanced technology. If it has an educated work force and stable political and economic conditions, the technological spillover is more likely to occur. Conversely, if its education system and institutions are not well developed, the new technology cannot be adopted. The income of the country will lag behind the income of countries with better education and institutions.

Diminishing returns. The second reason is that investments in the rich countries are less profitable than investments in the poor countries. Think of it as follows. If an accounting firm (in a rich country) has 10 computers, one more computer will make little difference. If an accounting firm (in a poor country) has no computers at all, then buying one computer would make a big difference. The investment in that first computer would pay off handsomely. Therefore, international investment would flow primarily from the rich countries to the poor countries where profits are greater. This inflow of investment will make poor countries richer.

However, returns could also be increasing, instead of diminishing. In the example above, if the firm has many computers and much experience using them, an additional computer will be put to good use. If it has only one computer, then it may not know what to do with it. In that version of the story, adding investments to already rich firms or countries is more profitable. Then, investment flows to them and makes them even richer. Incomes around the world diverge instead of converging.

What is the evidence? There is income convergence across countries that are already fairly affluent. For example, incomes have converged significantly in the European Union and other rich countries in North America and elsewhere. Looking more broadly, there is no evidence that the incomes of poor countries in Africa, Latin America and elsewhere have gained relative to the rich countries. In fact, when it comes to the poorest countries, there has even been some income divergence.