This is, of course, the subject of a great deal of controversy. There are many people who would argue that colonization was responsible for most of the lack of development in what used to be called the Third World. Let us look at two of the main arguments that can be made in this regard.
First, it can be argued that European colonization was a major cause of economic weakness in these countries after they became independent. When the Europeans colonized an area, they tended to run its economy for their own good rather than the good of the colony. They created colonial economies that were based on producing low-value goods (usually agricultural or mineral) for the colonial power. These economies were not encouraged to diversify or to develop. For this reason, they came to be very disadvantaged relative to rich world economies.
Second, it can be argued that European colonization stunted political development in the colonies. The Europeans often created “unnatural” states made up of multiple ethnic groups, some of which did not get along well. They often played one group off against the other. Even when this did not happen, they did not encourage the native peoples to gain the education and the experience that they needed to be able to run their own governments well. These factors meant that newly independent countries often had unstable political systems and have yet to overcome that handicap. Unstable and corrupt government makes economic development very difficult.
In these ways, we can argue that European colonization was mainly responsible for lack of economic development in the “Third World.”