Evidence would be hard to obtain. I find it highly improbable that any software development methodology can provide deterministic, repeatable results. The met

Evidence would be hard to obtain. I find it highly improbable that any software development methodology can provide deterministic, repeatable results. The metric to measure isn't productivity, rather one should be looking at happiness. If it works for your team and they feel like they get a lot done by using an agile approach then you're using the right methodology. Agile isn't for everyone though and that's not a failing of the methodology.