The development of a nation is often conflated with economic growth. However, while economic strength is certainly a country’s means of development, is it what ultimately determines how developed that country is? According to the United Nations’ Human Development Index (HDI), other factors such as human freedom should be the key in quantifying and evaluating development.

Based on the 2015 HDI, 24/7 Wall St. reviewed the most and least livable countries. Data from the Index is based on three dimensions of human progress: longevity, education, and financial stability. As was the case last year, Norway is the most livable country in the world, while Niger is the least livable.

A decent income can have a tremendous impact on standard of living. Healthy food, access to exercise facilities, insurance, and the education necessary to increase one’s position in life all have monetary costs. The U.N. used gross national income in its calculation of the HDI to reflect the standard of living in a country. In the most developed countries, gross income per capita is generally quite high. All of the world’s 10 most livable countries have among the top 30 gross national incomes per person. The top rated country, Norway, has the world’s sixth highest gross national income per capita of $63,909.

Click here to see the 25 least livable countries in the world.

Click here to see the 25 most livable countries in the world.

At the other end of the spectrum, the world’s least developed countries typically have very low incomes. Six of these 10 least livable nations are among the bottom 10 countries by gross national income per capita. The Central African Republic, which has the lowest gross national income per capita in the world at just $581, is the second least developed country worldwide. Niger, the least developed nation in the HDI, has gross income per capita of $908.

In the countries at the top of the HDI, large shares of the labor force are employed in relatively high-paying service sector jobs. In countries at the other end of the HDI, the vast majority of which are in Sub-Saharan Africa, the agriculture sector employees the bulk, if not the majority, of the labor force. According to the World Bank, agriculture employs 65% of Africa’s labor force, and accounts for nearly one-third of economic output from the continent.

While low-paying agricultural jobs largely explain the relatively low incomes in countries at the bottom of the HDI, the agriculture sector is still essential to the development of these nations. Ethiopia’s economy, for example, grew rapidly last year, and the country is one of the most dependent on the agriculture sector.

Education is not only the basis of economic prosperity, but also a key feature of personal fulfillment. Compared to emerging nations and other countries at the bottom of the HDI’s ranking, residents of the most livable countries tend to spend many more years in school. Germans, Brits, and Canadians spend around 13 years getting an education, on average, the most years of any country in the world. By contrast, residents of every country in Sub-Saharan Africa spend no more than six years in school on average. In Burkina Faso, Niger, and Chad, the typical resident spends less than two years in school.

Life expectancies, another factor considered in the Human Development Index, are also far higher in advanced economies. Japan, Singapore, and Switzerland, for example, each report life expectancies at birth of at least 83 years. By this metric, the United States is a relative laggard. The mean life expectancy at birth in the United States of 79.1 years is ranked just 36th worldwide.

Individuals born in the U.S. are still expected to live as many as two decades longer than babies born in many of the Sub-Saharan African nations at the other end of the HDI.

High fertility rates are also common in the 25 least developed nations. In all but one of these countries, women give birth at least three times over the course of their lives. In Burundi, Chad, and Nigeria, the fertility rate is over six births per woman. By contrast, in all of the 25 most developed nations, each woman gives birth fewer than two times on average. According to the UN, such high fertility rates are unsustainable not just because it presents barriers to lowering poverty, but also because a high, unstable birth rate will decrease the number of working-age individuals per capita.

To identify the most (and least) livable countries in the world, 24/7 Wall St. reviewed social and economic data covering 188 countries. All data was provided in the United Nations Development Programme’s Human Development Index, a report released annually for the past 25 years. Life expectancy at birth is provided by the UN Population Division in the UN Department of Economic and Social Affairs (UNDESA); mean years of schooling are based on UNESCO Institute for Statistics (UIS) educational attainment data and, for some countries, Barro and Lee (2013) methodology where UIS data are not available; expected years of schooling is provided by UIS; and GNI per capita (in 2011 $PPP) by the World Bank and the International Monetary Fund. For several countries, mean years of schooling is estimated from nationally representative household surveys and for some countries GNI was obtained from the UN Statistical Division’s database – National Accounts Main Aggregates Database.

These are the world’s least livable countries.