It’s no secret that the world’s population is on the move, but it’s rare to get a glimpse of where that flow is happening. In a study released in today’s Science, a team of geographers used data snapshots to create a broad analysis of global migrations (diagram below) over 20 years:

 An article on Quartz by Nick Stockton provides a bit more analysis by country. 

 Migration data is counted in two ways: Stock and flow. “The stocks are the number of migrants living in a country,” says Nikola Sander, one of the study’s authors. Stock is relatively easy to get—you just count who is in the country at a given point of time. Flow is trickier. It’s the rate of human traffic over time.

While the results of the migration study aren’t particularly groundbreaking, there are two interesting insights:

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1) Adjusted for population growth, the global migration rate has stayed roughly the same since around  since 1995 (it was higher from 1990-1995).

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2) It’s not the poorest countries sending people to the richest countries, it’s countries in transition—still poor, but with some education and mobility—that are the highest migratory contributors.

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“One of the conclusions they make in the paper, is the idea as countries develop, they continue to send more migrants, and at some point they become migrant-receiving regions themselves,” says Fernando Riosmena, a geographer from the University of Colorado, who did not contribute to this research, but is collaborating with one of the authors on a future paper.

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A few other noteworthy results:

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1) The largest regional migration is from Southeast Asia to the Middle East. This is largely driven by the huge, oil-driven, construction booms happening on the Arabian Peninsula.

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2) The biggest flow between individual countries is the steady stream from Mexico to the US. (In fact, the US is the largest single migrant destination)

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3) There’s a huge circulation of migrants among sub-Saharan African countries. This migration dwarfs the number leaving Africa, but the media pay more attention the latter because of the austerity-driven immigration debates in Europe.