What drives human migration?

It's often stated that migration is driven by big economic differences and underdevelopment and poverty in origin countries. And although that does play a role, that is not enough to understand migration as we see it in the world. To give you one example, most migration does not occur from the poorest countries. We actually see highest levels of both out- and in-migration in countries that have medium levels of development. And generally, our research shows that development processes tend to increase migration rates. Because development gives people the means, the capabilities to move around. Because in order to migrate, you need to have access to certain resources. And secondly, if people get better schooling, it often raises their aspirations in terms of what they want to achieve in life. And if those aspirations can't be fulfilled, they are where they live. People tend to aspire to migrate. And these are some of the explanations besides infrastructure, which is often better in more developed countries, why high-developed countries tend to be more migratory than the poorest countries in the world.