If someone is unemployed that can barely hold a keyboard without dropping it calling himself a software engineer is out of a job is counted it gets a lot harder though.
You can stick labels fairly easily on the various degrees, they may not mean much in terms of practical knowledge but they do put up a lower boundary that they had to cross. For auto-didacts you run the gamut all the way from incompetent bumbler to ace, and there is no foolproof way to separate those when looking at large groups but it will make a huge difference to the outcome of the study.
Especially in the IT sector there is a lot of "I am an 'x'" where X is anything from the set of recent buzzwords.
So I don't think you can make even that comparison in an easy and reliable way, what people call themselves may not be what they actually are.
You can stick labels fairly easily on the various degrees, they may not mean much in terms of practical knowledge but they do put up a lower boundary that they had to cross. For auto-didacts you run the gamut all the way from incompetent bumbler to ace, and there is no foolproof way to separate those when looking at large groups but it will make a huge difference to the outcome of the study.
Especially in the IT sector there is a lot of "I am an 'x'" where X is anything from the set of recent buzzwords.
So I don't think you can make even that comparison in an easy and reliable way, what people call themselves may not be what they actually are.