A country's national income often has a massive impact on its level of human development and the overall quality of life its residents enjoy. The World Bank, an international organization dedicated to helping countries overcome poverty, examines the GNI (Gross National Income) per capita of each of the world's countries and territories, then sorts each into one of four World Bank Country Lending Groups: high-income, upper-middle-income, lower-middle income, and low-income. Upper-middle income countries and lower-middle income countries are known collectively as middle-income countries (MICs). In response to shifts in the global economy, the World Bank adjusts the boundary lines between the categories each July.
2022-2023 World Bank Country Lending Group guidelines (all values USD):
- Low-income economies — 2021 GNI per capita of up to $1,085
- Lower-middle-income economies — 2021 GNI per capita of $1,086 to $4,255
- Upper-middle-income economies — 2021 GNI per capita of $4,256 to $13,205
- High-income economies — 2021 GNI per capita of $13,206 or more
Lower-Middle-Income Economy Countries:
Upper-Middle-Income Economy Countries:
| Albania | Cuba | Kazakhstan | Paraguay |
| American Samoa | Dominica | Kosovo | Peru |
| Argentina | Dominican Republic | Libya | Russia |
| Armenia | Ecuador | Malaysia | Saint Lucia |
| Azerbaijan | Equatorial Giunea | Maldives | Saint Vincent and the Grenadines |
| Belarus | Fiji | Marshall Islands | Serbia |
| Belize | Gabon | Mauritius | South Africa |
| Bosnia and Herzegovina | Georgia | Mexico | Suriname |
| Botswana | Grenada | Moldova | Thailand |
| Brazil | Guatemala | Montenegro | Tonga |
| Bulgaria | Guyana | Namibia | Turkey |
| China | Iraq | North Macedonia | Turkmenistan |
| Colombia | Jamaica | Palau | Tuvalu |
| Costa Rica | Jordan |
More than half of the world's countries are middle-income countries, which display a diverse range of regions, sizes, populations, and cultures. MICs are home to 75% of the world's population, including 62% of its poor, and produce one-third of the global GDP. Many MICs face similar challenges, which often include population growth that outpaces the development of infrastructure, a lack of investment capital and skilled workers, and government corruption and/or instability.
Middle-income countries are essential to global economic growth. Development and growth in MICs, according to the World Bank, can result in benefits including increased international trade, greater sustainable energy development, improved food and water security, and a reduction in border conflicts, which can ripple out to other countries as well. If evaluated using the United Nations' overarching Human Development Index, middle-income countries tend to classify as developing countries, ranking above least-developed countries (which typically correlate to low-income countries) but falling short of developed (high-income) countries.