WRT the topic "How common are jobs for open source R&D?"
I'm not sure about why I am asking for clarification.
The canonical link from days of old for this is: Are Career Advice questions useful to anyone except the poster?
Career advice is one of our perpetual problems on programmers. The essence of the career advice close reason is that any information is very particular to the person asking. In days of old, these would often be closed as "too localized" - either they are asking about too narrow a person (themselves), too narrow a time, or too narrow a locality.
This question has two issues with it. The first is that 'too narrow' in time and location. Questions asking for information about job opportunities is highly location and time dependent. You'd get very different answers when asking for different times or locations.
I will point out that you tagged this as job-market - which a rough look through shows a lot of closed questions. This should have been a warning that this question is problematic.
The question about economics and market theory? That isn't exactly our area of expertise. It might have been ok on Economics.SE but that was closed for lack of activity a couple of years ago. Such a question is... I could see opinion and also the off topic (career advice), or a custom reason. It really doesn't look for a good fit.
The other half of the question that is in the lead in:
I would like some statistics if possible, or educated guesses if statistics are not possible.
Asking for stats is also a difficult area. The answers that you get to this are either polling type responses:
The company I work for had a half dozen open positions for linux kernel engineer a year ago
The company I work for doesn't touch open source with a 10' pole.
These type of 'spot polling' answers often show up with requests for stats or guesses. They are poor answers and questions that encourage such answers tend to get closed.
The other side of the asking for stats is that it makes the people answering the question into research librarians rather than expert programmers and software architects. It asks us to use google for you, a crowdsourced search engine. This doesn't draw upon our expert advice and information.
Career advice may not have been the best choice for a close reason. But the question really isn't a good fit for Programmers.SE being a mix of economics, stats request, and a bit of career information too. Career advice was likely the most convenient choice for the close reason.