Years passed since Scrum had been widely adopted in software world. I’m wondering if there is any efficiency survey done by more or less independent people/institutes. Obviously scrums gurus who travel around the globe giving lectures and training always find numbers of excellent showcases, however I’d rather listen someone who doesn’t sell Scrum.
By efficiency I mean total productivity (delivered value/cost), but not some internal characteristics like communications inside teams and so on.
Update based on discussion in comments:
One of the ways to do such survey/analysis could be based on comparison of similar projects developed with Scrum and without Scrum. I believe even 10 years ago there were projects similar to some current. Of course, it does not make sense if applied technologies are completely different, so these projects have to be implemented on same/similar technology.