> 20 years of experience people to be principal engineers and only 5% of roles are principal jobs, then after 20 years 95% of engineers need to leave the industry.

I'm not sure I follow your math. 5% of roles are principal jobs, but devs with 20+ years are not 100% of the talent pool. This doesn't hold up if devs with 20+ years are are 5% or less of the talent pool.

You're right - my comment was sloppy!

Still, given "20+ years of experience" represents all programmers of ages, say, 45-65 - or two decades worth of CS graduates - I feel that cohort far exceeds the market for principals? If you think it is smaller, maybe that's because everyone who wasn't in the top n% had to leave?

Although other commenters have pointed out that the growth of the industry counters that, that won't last forever!

I thought it was an interesting question and found this page[1] . It is a survey of 50k devs on Stack overflow. 3.8% percent of those surveyed were over 50. Cenensus data here[1] gives ~20% over 50

https://www.freecodecamp.org/news/2-out-of-3-developers-are-...

https://datausa.io/profile/soc/15113X/#about

Is fair to say we have an up and out culture like big law, consulting and finance?

Yes, but nobody under 35 realises they're perpetuating it until its their ass getting upped and outed like everyone else

I agree with the sentiment, but in this industry which has exponential growth, the number of people in it doubles every 5 years, I think. So if you've been working 20 years, there are now 16x as many people as when you started...so you are in the most senior 6% of people if you managed to stick around.

Except after 20 years in the industry, there's a vast amount more work available...And the industry is still running at a shortage of tech. people.

(oddly enough, the 'average' programmers entire career was 10 years last I checked. People seem to burn out and move on..)