Hardly enough time to even know the impact and costs of what you developed and shipped. Kind of makes you wonder what type of work force you're creating when a large percentage of them are constantly leaving. Maybe for ICs this isn't a concern compared to Directors, VPs, or maybe Staff SEs?
[1] https://www.payscale.com/data-packages/employee-loyalty/full...
[2] https://buffer.com/resources/employee-tenure/
[3] https://www.bizjournals.com/sanfrancisco/news/2019/10/17/thi...
I mean it intuitively kind of makes sense. If you work in a city with many other high paying prestigious jobs, why wouldn't you job hop? There's little risk, whereas if you were in a city that had very few prospects you'd probably stick around longer.
I live in Boston and I jump around every year'ish getting more salary at each place I've worked at. If you worked at Google (or any other prestigious company), I imagine it's far far easier interviewing else where. Especially if you jump from prestigious company to prestigious company.
I figured people will always need devs and people really blow the "job hopper" thing out of proportion. Every job hopper I know makes a lot of money and they never struggled to find jobs. If anything they seem to have the best jobs from what I see.