What do you believe the motivation is behind corruption?

Why do people engage in corrupt practices? It can get them in a lot of trouble and often cost them large portions of their lives in prison, yet they do it anyway. It is particularly corrupt in the United States and other countries where capitalism is the economic system. Do you think this choice of an economic system has anything to do with the prevalence of corruption?
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Why is it more prevalent in countries where Capitalism is the economic system?
What do you believe the motivation is behind corruption?
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