The term Third World' was first used during the post-war years to refer to the less economically advanced countries of Asia, Africa and Latin America.
Not all the members of the Non-Aligned Movement were Third-World countries, but most of them were.
At the end of the 1970s, more than 100 countries were considered to be part of the Third World. Almost all of them were former colonies, and 2000 million people lived in them.
R. Palmer and J. Colton
Historia contemporánea,
Akal (Translated)