Some people use the excuse of colonialism to explain Third World poverty, but that's nonsense. Some the world's richest countries are former colonies: United States, Canada, Australia, New Zealand and Hong Kong. Some of the world's poorest countries were never colonies, at least for not long, such as Ethiopia, Liberia, Tibet and Nepal. Pointing to the U.S., some say that it's bountiful natural resources that explain wealth. Again nonsense. The two natural resources richest continents, Africa and South America, are home to the world's most miserably poor. Hong Kong, Great Britain and Japan, poor in natural resources, are among the world's richest nations.
We do not fully know what makes some societies more affluent than others; however, we can make some guesses based on correlations. Rank countries according to their economic systems. Conceptually, we could arrange them from those more capitalistic (having a large market sector and private property rights) to the more socialistic (with extensive state intervention, planning and weak private property rights). Then consult Amnesty International's ranking of countries according to human rights abuses going from those with the greatest human rights protections to those with the least. Then get World Bank income statistics and rank countries from highest to lowest per capita income.
Having compiled those three lists, one would observe a very strong, though imperfect correlation: Those countries with greater economic liberty and private property rights tend also to have stronger protections of human rights. And as an important side benefit of that greater economic liberty and human rights protections, their people are wealthier. We need to persuade our fellow man around the globe that liberty is a necessary ingredient for prosperity.