I think it's just too difficult a problem to distill down into a single metric. I did CS and Math for my undergrad and I was in the PhD program for CS but left with my MSc. My focus was on design and analysis of algorithms and based on that training, in my 3 years of professional activity (2 at a NASA contractor) I've run into very few problems that compared to the kind of work I did in my thesis. I think lines of code is one metric - but a really high number could actually be a sign of a really bad programmer! So, it's an inherently noisy signal. I think you have to look at successful projects completed and individual roles in those projects and judge that way.