It doesn't matter what I think. It's the UN that classifies nations, e.g. the G8.
Economic classification of nations and criteria: http://www.un.org/en/development/desa/policy/cdp/ldc/ldc_criteria.shtml
The economically underdeveloped countries of Asia, Africa, Oceania, and Latin America, considered as an entity with common characteristics, such as poverty, high birthrates, and economic dependence on the advanced countries. The French demographer Alfred Sauvy coined the expression ("tiers monde" in French) in 1952 by analogy with the "third estate," the commoners of France before and during the French Revolution-as opposed to priests and nobles, comprising the first and second estates respectively. Like the third estate, wrote Sauvy, the third world is nothing, and it "wants to be something." The term therefore implies that the third world is exploited, much as the third estate was exploited, and that, like the third estate its destiny is a revolutionary one. It conveys as well a second idea, also discussed by Sauvy, that of non-alignment, for the third world belongs neither to the industrialized capitalist world nor to the industrialized Communist bloc. The expression third world was used at the 1955 conference of Afro-Asian countries held in Bandung, Indonesia. In 1956 a group of social scientists associated with Sauvy's National Institute of Demographic Studies, in Paris, published a book called Le Tiers-Monde. Three years later, the French economist Francois Perroux launched a new journal, on problems of underdevelopment, with the same title. By the end of the 1950's the term was frequently employed in the French media to refer to the underdeveloped countries of Asia, Africa, Oceania, and Latin America.
Characteristics
The underdevelopment of the third world is marked by a number of common traits; distorted and highly dependent economies devoted to producing primary products for the developed world and to provide markets for their finished goods; traditional, rural social structures; high population growth; and widespread poverty. Nevertheless, the third world is sharply differentiated, for it includes countries on various levels of economic development. And despite the poverty of the countryside and the urban shantytowns, the ruling elites of most third world countries are wealthy.
This combination of conditions in Asia, Africa, Oceania and Latin America is linked to the absorption of the third world into the international capitalist economy, by way of conquest or indirect domination. The main economic consequence of Western domination was the creation, for the first time in history, of a world market. By setting up throughout the third world sub-economies linked to the West, and by introducing other modern institutions, industrial capitalism disrupted traditional economies and, indeed, societies. This disruption led to underdevelopment.
Because the economies of underdeveloped countries have been geared to the needs of industrialized countries, they often comprise only a few modern economic activities, such as mining or the cultivation of plantation crops. Control over these activities has often remained in the hands of large foreign firms. The prices of third world products are usually determined by large buyers in the economically dominant countries of the West, and trade with the West provides almost all the third world's income. Throughout the colonial period, outright exploitation severely limited the accumulation of capital within the foreign-dominated countries. Even after decolonization (in the 1950's, 1960's, and 1970's, the economies of the third world developed slowly, or not at all, owing largely to the deterioration of the "terms of trade"-the relation between the cost of the goods a nation must import from abroad and its income from the exports it sends to foreign countries. Terms of trade are said to deteriorate when the cost of imports rises faster than income from exports. Since buyers in the industrialized countries determined the prices of most products involved in international trade, the worsening position of the third world was scarcely surprising. Only the oil-producing countries (after 1973) succeeded in escaping the effects of Western, domination of the world economy.
No study of the third world could hope to assess its future prospects without taking into account population growth. In 1980, the earth's population was estimated at 4.4 billion, 72 percent of it in the third world, and it seemed likely to reach 6.2 billion, 80 percent of it in the third world, at the close of the century. This population explosion in the third world will surely prevent any substantial improvements in living standards there as well as threaten people in stagnant economies with worsening poverty.