The number of software developers has maybe doubled in the last 20 years. The number of senior developers has "always" been low, because the field suffers from unusually high attrition. Many people find that software is not for them, many switch fields after losing their jobs in an economic downturn, some move to management, and some make too much money to bother continuing until retirement age.

Has there actually been attrition? Exponential growth is enough to explain "many more juniors than seniors" at any time in the past, present or future.

Also for attrition to be the cause, you'd need a lot more seniors dropping off than juniors.

The exponential growth has been something like 3-4%/year, or 2x in 20 years. Though it's hard to find useful statistics that take different job titles and changing nature of the industry properly into account.

If you had asked me in 2010, I would have said that the median software developer lasts 5-10 years in the industry. A lot of people left the field after the dot-com bubble burst. The same happened again in a smaller scale in the late 2000s, at least in countries where the financial crisis was a real-world event (and not just something you heard about in the news). But now there has been ~15 years of sustained growth, and the ratio of mid-career developers to juniors may even be higher than usual.

None of my friends who graduated with me are still software developers and I’m several years from retirement age.

There’s a bunch of filters. Many people quickly realize they don’t enjoy development, next is openings in management. One of the big ones is at ~40 you’re debt free, have a sizable nest egg, and start thinking of you really want to do this for the next 20 years?

A part of this is the job just keeps getting easier over time. Good developers like a challenge, but realize that the best code is boring. Tooling is just more robust when you’re doing exactly the same things as everyone else using it, and people can more easily debug and maintain straightforward code. So a project that might seem crazy difficult at 30 starts to just feel like a slog through well worn ground.

Having significant experience in something also becomes a trap as you get rewarded for staying in that bubble until eventually the industry moves on to something else.

I recently hit thirty years of professional software development, in companies large small, profit and non profit, proprietary and FOSS, I have led teams of forty, sat in a corner as the only developer and one thing I know in my bones - I love making software and money just means I get to code what I want instead of what The Man wants.

In fact I already have my retirement planned - a small near flat in Argostolli, a walk down to the coffee bars on the harbour and a few hours adding code and documentation to a foss project of my choice before heading to the beach with grandkids.

Now affording retirement might be interesting but not having coding in it will be like not having reading and writing

You're probably from a privileged environment such as working in the US (probably in a top location) and probably from a top university or you were there at the right time to join a top company as it grew rapidly.

The first paragraph probably applies to 1-10% of developers worldwide...

The only part of that that applies to my friends is living in the US. Programming pays well just about anywhere for that area even if the absolute numbers are less extreme.

I also don’t mean early retirement. Still, combine minimal schooling, high demand, reasonable pay, and the basic financial literacy of working with complex systems adds up over time.

Yeah, there is no way that the majority of EU-based developers can retire at 45 on their meagre salaries.

I'm reasonably sure that this estimate is far off the mark. The numbers I've seen suggest that the number of new software developers entering the industry has doubled every five years since at least the mid 90s. That's not the same metric as total number of developers, but it may as well be, and it definitely doesn't add up to a mere doubling of the total in twenty years.