As a hiring manager or recruiter, it’s tempting to think that job candidates will want to stay at marquee firms for as long as possible. The idea certainly makes sense: once you’ve gotten your foot in the door at Google or Facebook, why wouldn’t you stay forever—or at least until your stock fully vests? But new data from Paysa suggests that tech pros at some of the world’s most prominent firms don’t stick around very long at all. The employee-resource firm recently analyzed its database, isolating top tech companies, then distilled the list further into two groups: titans and disruptors. “We defined titans as public companies that had their IPO over 10 years ago, with a current valuation of over $100 billion, and tech disruptors as privately held companies or public companies that had their IPO in the last 10 years, whose current valuation is over $10 billion,” the company wrote in a blog posting. (The actual companies included Facebook, Google, Oracle, Apple, Amazon, Twitter, Microsoft, Airbnb, Snap Inc., and Uber.) The number-one job at each of these companies is “Software Engineer.” Jobs vary from there, but the top five positions at each company were in tech. Because of that, we’re comfortable that Paysa’s figures represent tech workers and jobs in tech. If you want a job at those big firms for longer than two years, Facebook is your only safe bet: its employees last an average of 2.02 years. And Facebook is far and away the winner: Google employees last about 1.9 years, while Apple engineers can expect to be there 1.85 years. In terms of retention, that's pretty short. These figures don’t improve with ‘disruptors,’ either: Airbnb, Snap Inc. and Uber all rate lowest on this list. Uber employees last an average of 1.23 years, making the startup clearly and distinctly the worst place to work on Paysa’s tenure list. Longevity seems even worse when you count the days. Facebook engineers stick around about 737 days. Googlers get 693 days or so. Apple employees will be at the spaceship around 675 days. The numbers get alarming when you reach the bottom of the list: Airbnb and Snap Inc. dip below 600 working days. Uber was the only company where employee retention dipped below 500 days – but if you’ve got 449 days to waste, we’ve got just the place for you to work. Many of these top companies are staffed by relative newcomers. Snap, Oracle, Microsoft and Apple all have large percentages of employees with less than two years’ experience. Facebook and Amazon fare better (2-5 years), while Google, Uber, AirBNB and Twitter all have seasoned vets (6-10 years experience). Why is turnover so high? It’s easy to pin some of it on these large tech companies being a first job. Having put a well-known company on their C.V., young engineers may feel the urge to strike out and make their mark on their own startup, or a smaller company where they can potentially have a bigger impact on cutting-edge tech. The converse is also interesting: why is Uber, with all its funding and high-profile reputation, having a hard time hanging onto engineers? (We have a few ideas.) In a broader context, Paysa’s findings underline a key challenge for recruiters and hiring managers: tech pro retention rates, especially at a time of notably low unemployment within the industry. Even the largest and well-monetized firms will need to do a lot to convince highly specialized tech pros to stay for longer than a few years.