Don't want to guess at numbers but my gut instinct & experience tells me that very few physicists end up doing physics and most end up in finance, software, and hardware.
803 responses, 297 in potentially full-time positions.
62% (of all physics phds employed at potentially full-time positions) in non-physics field, break down by industry:
Engineering - 20%
Computer software - 14%
Business or Finance - 11%
Other sciences - 8%
Education - 2%
Medical services - 2%
Other - 5%
The computer industry is notoriously unstable with jobs often quite short term in practice, with layoffs common.
Just to be clear, the referenced AIP report starts with the phrase:
Positions accepted by PhD degree recipients following receipt of their
degrees fall into three categories: postdoctoral fellowships, potentially
permanent positions and other temporary positions.
The figure on page two of the AIP report specifically lists a "private sector" block under "potentially permanent".
Tabel 1 on page 3 lists 70 percent of potentially permanent positions as "private sector." Again this is very misleading as private sector positions are potentially permanent only is the sense that there is a small chance that you might continue at the same employer until retirement; there is nothing like a guarantee.
To me "potentially permanent" seems like a serviceable phrase to encompass positions in academia and in industry that do not have an end data built in to them. It contrasts them to "temporary" positions like postdocs in academia or contractors in industry where you know going into the job that your employment ends on a certain date.
The primary audience for a report on outcomes for Ph.D.'s in Physics one year after graduation, getting their Ph.D. degree, is students (and parents of students) evaluating whether to pursue a Ph.D.. Obviously, they should investigate longer term outcomes, but young people often don't, focusing the next step in their life/career.
Potentially permanent position sounds like a general version of "tenure track research job" as another commenter correctly noted below.
Students with little or no work experience often do not have an accurate impression of salaries, working conditions, and other aspects of the work world (or academia), specifically in the private sector computer industry where most Ph.D's in Physics currently end up.
News coverage of computer companies like Google emphasizes many far out research-like projects such as the Google self-driving car, the AlphaGo deep learning project, and so forth. These sounds like academic research, so why wouldn't these companies have comparable positions to tenure track research jobs? Indeed, in very rare cases, they may have such positions.
However, the vast majority of industry jobs are at will full time jobs without a specified end date. Especially in the computer industry, they are quite insecure and often short-lived, very different from what potentially permanent position implies. They are not analogous to tenure track jobs.
My job is described as permanent full time, because my contract is ongoing, and I work 40 hours a week; when I was a student, I had a permanent part time job.
This is in contrast to a casual job, which in New Zealand is similar to at-will (but with strong restrictions on what roles can be casual); or a fixed term contract.
In any case, with the closure or heavy cutbacks at corporate research labs, AIP should update its language to reflect current realities.
For a few years, he started checking the median age of physics professors, and noticed it went up every year instead of down. Tenured profs decided to stay in their seats instead of retiring, and there were no new positions being created for young professors. That was his indication to get out (this was during the mid 90s).
The real crux of the problem is that modern PhD programs were originally designed post WW2, in the era of the GI bill and fast expansion of college education where there was high demand for new professors. That's no longer the case, but we still train PhDs as if they would get a job even though most won't.
Still, it seems low IMHO. Unless you start counting at the point where the person gains full tenure rather than from the point where they become some kind of "group leader", "assistant professor", or such "tenure track" type position?
Why? I know an academic who has done exactly that. Nearing retirement now.
Does physics academia really not have another position you can promote someone to, if you want to keep paying them to do research for you, but they've "timed out" of the postdoc role? I had assumed this kind of research-scientist role wasn't CS-specific, since it's existed for a while, and at big universities, CS hasn't traditionally had the clout to invent completely new job titles, so hiring is usually mapped onto stuff that exists in some form or another at the institutional level.
Eventually you need the money for retirement...
Unfortunately, becoming a developer is a short-term optimal choice that you pay for in the long term.
The 40-year-old physicist has tenure and can work on whatever he wants. As far as his peers are concerned, he's mid-career. The 40-year-old programmer is considering plastic surgery so he can still get hired in the Valley.
The people who become developers find out that they don't have permission to get a day older than 35 unless they can make it into management. And if you were going to be a manager anyway, you might as well have gotten an MBA in your mid-20s, and then you'd be making far more than the developer would even dream of.
Coding was always way more fun than doing 4th year/grad school level physics for me too.
Programming is a lot of fun, but most software jobs aren't programming intensive. The coding is trivial and a high school student could do most of the work. The hard part is dealing with tickets, PMs, and unnecessary meetings.
For me it was also that nothing truly new was being discovered in my area of physics, so it all felt a bit boring.
Plus the politics that comes when post docs have to fight and plot over rare tenured positions when they appear.