A developing country, also called a less developed country or an underdeveloped country, is a nation or a sovereign state with a less developed industrial base and a low Human Development Index (HDI) relative to other countries. There are no universally agreed-upon criteria for what makes a country developing versus developed and which countries fit these two categories, although there are general reference points such as a nation's GDP per capita compared with other nations. Also the general term less-developed country should not be confused with the specific least developed country. The term "developing" describes a currently observed situation and not a dynamic or expected direction of progress. Since the late 1990s developing countries tended to demonstrate higher growth rates than the developed ones. An alternative measurement that has been suggested is that of gross national happiness. Countries on the boundary between developed and developing are often categorized under the term "newly industrialized countries".
According to authors such as Walt Whitman Rostow developing countries are in transition from traditional lifestyles towards the modern lifestyle which began in the Industrial Revolution in the 18th and 19th centuries.
Various terms are used for whatever is not a developed country. Terms used include less developed country or less economically developed country, and for the more extreme, least developed country or least economically developed country.
Criteria for what is not a developed country can be obtained by inverting the factors that define a developed country:
Kofi Annan, former Secretary General of the United Nations, defined a developed country as "one that allows all its citizens to enjoy a free and healthy life in a safe environment." But according to the United Nations Statistics Division,
The UN also notes,
On the other hand, according to the classification from International Monetary Fund (IMF) before April 2004, all countries of Central and Eastern Europe (including Central European countries that still belongs to the "Eastern Europe Group" in the UN institutions) as well as the former Soviet Union (USSR) countries in Central Asia (Kazakhstan, Uzbekistan, Kyrgyzstan, Tajikistan and Turkmenistan) and Mongolia, were not included under either developed or developing regions, but rather were referred to as "countries in transition". They are however widely regarded (in the international reports) as "developing countries".
The IMF uses a flexible classification system that considers "(1) per capita income level, (2) export diversification--so oil exporters that have high per capita GDP would not make the advanced classification because around 70% of its exports are oil, and (3) degree of integration into the global financial system."
The World Bank classifies countries into four income groups. These are set each year on July 1. Economies were divided according to 2016 GNI per capita using the following ranges of income:
Since 2016 the World Bank no longer divide countries into two groups according to the out-dated concept of developed and developing 
Along with the current level of development, countries may be classified by how much this has changed over some amount of time. This may be by absolute numbers or country ranking.
The development of a country is measured with statistical indexes such as income per capita (per person), (gross domestic product) per capita, life expectancy, the rate of literacy, freedom index and others. The UN has developed the Human Development Index (HDI), a compound indicator of some above statistics, to gauge the level of human development for countries where data is available. The UN sets Millennium Development Goals (MDGs) from a blueprint developed by all of the world's countries and leading development institutions, in order to evaluate growth.
Developing countries are, in general, countries that have not achieved a significant degree of industrialization relative to their populations, and have, in most cases, a medium to low standard of living. There is a strong association between low income and high population growth.
The terms utilized when discussing developing countries refer to the intent and to the constructs of those who utilize these terms. Other terms sometimes used are less developed countries (LDCs), least economically developed countries (LEDCs), "underdeveloped nations" or Third World nations, and "non-industrialized nations". Conversely, developed countries, most economically developed countries (MEDCs), First World nations and "industrialized nations" are the opposite end of the spectrum.
To moderate the euphemistic aspect of the word developing, international organizations have started to use the term less economically developed country (LEDCs) for the poorest nations--which can, in no sense, be regarded as developing. That is, LEDCs are the poorest subset of LDCs. This may moderate against a belief that the standard of living across the entire developing world is the same.
The concept of the developing nation is found, under one term or another, in numerous theoretical systems having diverse orientations -- for example, theories of decolonization, liberation theology, Marxism, anti-imperialism, and political economy.
Another important indicator is the sectoral changes that have occurred since the stage of development of the country. On an average, countries with a 50% contribution from the Secondary sector of Manufacturing have grown substantially. Similarly countries with a tertiary Sector stronghold also see greater rate of Economic Development.
Some researchers in development economics, such as Theodore Schultz who won a Nobel Prize in 1979, have found that literate farmers in developing countries are more productive than illiterate farmers. They therefore recommend investing in human capital (education, health, etc.) as an effective tool for economic development. Others, such as Mohammed Tamim, believe that economic development is measurable in educational level from primary school to the university. They noticed that wherever the educational level is raised, the level of development is also raised. They conclude that the percentage of the schooled population is proportional to the economic growth rate and inversely proportional in the demographic growth rate. The Take-Off of Walt Whitman Rostow can start in a country if its population is completely schooled. It is therefore necessary for the organization of a worldwide education program, itself conditioned by another worldwide program of birth control and the establishment of a worldwide organization for the implementation of this development strategy.
This section is in a list format that may be better presented using prose. (September 2016)
The following list shows the most significant environmentally-related causes or conditions, as well as certain diseases with a strong environmental component:
There are several terms used to classify countries into rough levels of development. Classification of any given country differs across sources, and sometimes these classifications or the specific terminology used is considered disparaging. Use of the term "market" instead of "country" usually indicates specific focus on the characteristics of the countries' capital markets as opposed to the overall economy.
Developing countries can also be categorized by geography:
Other classifications include:
There is some criticism of the use of the term "developing country". The term implies inferiority of a "developing country" or "undeveloped country" compared with a "developed country", which many countries dislike. It is criticized for being too positive and too negative.
It assumes a desire to "develop" along the traditional Western model of economic development, which a few countries, such as Cuba and Bhutan, choose not to follow.
The concept of "development" rests on the assumption that Modernization theory holds. Modernization theory, as the dominant development theory of the late 19th and 20th centuries, has largely contributed to the definition of "development". In short, it argues that there is only one way to achieve "modernity" and "development" - that of "Western" nation-states. Largely challenged today, modernization theory still holds an important role in defining "development".
The term "developing" implies mobility and does not acknowledge that development may be in decline or static in some countries, particularly in southern African states worst affected by HIV/AIDS. In such cases, the term "developing country" may be considered a euphemism. The term implies homogeneity between such countries, which vary widely. The term also implies homogeneity within such countries when wealth (and health) of the most and least affluent groups varies widely. Similarly, the term "developed country" incorrectly implies a lack of continuing economic development/growth in more-developed countries.
In general, development entails a modern infrastructure (both physical and institutional), and a move away from low value added sectors such as agriculture and natural resource extraction. Developed countries, in comparison, usually have economic systems based on continuous, self-sustaining economic growth in the tertiary sector of the economy and quaternary sector of the economy and high material standards of living. However, there are notable exceptions, as some countries considered developed have a significant component of primary industries in their national economies, e.g., Norway, Canada, Australia. The USA and Western Europe have a very important agricultural sector, and are major players in international agricultural markets. Also, natural resource extraction can be a very profitable industry (high value added), e.g., oil extraction.
An alternative measurement that has been suggested is that of gross national happiness, measuring the actual satisfaction of people as opposed to how fiscally wealthy a country is.
During the late 20th century, and with the advance of World-systems theory, the notions of "developed country" and "developing country" have started to slowly be replaced by the less-controversial, trade-based, notions of "core country", "semi-periphery country" and "periphery country".
Countries not listed by IMF
The following, including the Four Asian Tigers and new Eurozone European countries, were considered developing countries until the '90s, and are now listed as advanced economies (developed countries) by the IMF. Time in brackets is the time to be listed as advanced economies.
Three economies lack data before being listed as advanced economies. Because of the lack of data, it is difficult to judge whether they are advanced economies or developing economies before being listed as advanced economies.