There are many hypotheses about what may cause international inequality. For example, poor countries may have been subjected in the past or present to exploitation, colonialism, neocolonialism or imperialism. In this context, the dependency theory, the Marxian point of view on imperialism and even the anti-globalization movement may be relevant. New institutional economists, like Douglass North, emphasize the role of certain institutions, like those protecting property rights, in the development of rich nations. Other economists think that internal national inequality and corruption may also be important factors in underdevelopment. Many other causes may play a role, as it is case in poverty. With very limited success, even national mean IQ differences have been proposed as hypothetical causes (see IQ and the Wealth of Nations).

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