There's a lot of talk right now about the impact of immigrants on American jobs. In reality, however, the real bogeyman when it comes to displacing workers isn't immigrants -- it's robots.

Case in point: Amazon's (NASDAQ:AMZN) vast network of fulfillment centers is using 45,000 robots to help it pick, sort, and ship units faster. The robots are made by Kiva Systems, which was acquired by the online retail giant for $775 million in 2012.

"Amazon has long used automation in its fulfillment centers, and Kiva's technology is another way to improve productivity by bringing the products directly to employees to pick, pack and stow," said an Amazon executive when the deal was announced.

Since purchasing Kiva, Amazon has rapidly scaled up the number of robots it uses in its distribution system, adding approximately 15,000 a year.

A bar chart showing the number of robots that work in Amazon fulfillment centers.

Data sources: USA Today, Seattle Times, Wired. Chart by author.

And Amazon is just one example of a company that's turning to robots to increase speed, accuracy, and efficiency. There are self-service checkout counters at grocery stores. Robo advisors are helping investors save for retirement. And if you go into a McDonald's nowadays, you'll find self-service kiosks, and even a Big Mac ATM, that eliminate the need for cashiers.

Bill Gates even went so far recently to suggest that robots should pay income taxes. "If a human worker does $50,000 of work in a factory, that income is taxed," said Gates. "If a robot comes in to do the same thing, you'd think we'd tax the robot at a similar level."

In short, people have a right to be worried about jobs in the future, but if you're looking for someone to blame for the trend, then you'll need to find a robot.

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John Maxfield has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Amazon. The Motley Fool has a disclosure policy.