GDP, GNP, and GNI per Capita

A country's total economy can grow while ordinary people see none of it, because total output and income per person are two different numbers. If a nation's economy expands but its population grows just as fast, or if the gains concentrate in a few hands, average income per person barely moves. That gap between the size of an economy and the wellbeing of its people is exactly what per capita measures are built to expose.

GDP, gross domestic product, is the value of all goods and services produced within a country's borders, no matter who owns the businesses. GNP, gross national product, is the value produced by a country's citizens and companies, no matter where in the world they are working. GNI, gross national income, is closely related to GNP but tallied as income rather than output, and it is the figure most commonly divided by population today. Dividing any of these totals by population gives a per capita figure, an average slice of the economic pie per person.

These measures sit at the center of ranking development alongside Rostow's stages and Wallerstein's core-periphery model, because economists need some number to sort countries by wealth before asking harder questions about health, education, and equality. A rising GDP or GNI per capita is a useful first signal, but it is only a starting point. The next step in studying development is asking what these income numbers leave out, which is where composite measures like the Human Development Index come in, since they add life expectancy and education to income.