Comment New code vs old code (Score 4, Insightful) 121
I suspect a significant difference is the Rust developers are probably working on something newer than the C++ developers. The quickest things to switch to Rust will be the smallest/newest products. The large, creaky, 1-billion-edge-cases C++ code is going to be the last stuff moved.
First, working on newer code bases is much more productive (see 1-billion-edge-cases)
Second, working on newer code bases is usually more interesting. Which means more of the better developers are going to successfully push to get on those projects. The fact that it's in a language that's getting extra buzz at the moment is going to accelerate that.
Better developers on a better code base are going to have a leg up on productivity, regardless of the language used. So while I don't doubt Rust is "more productive", I am going to doubt "double".