Difficulty of project/task seemingly is a big factor. The engineer working in a legacy code base is likely to be less productive due to technical constraints.

How to grade that into any kind of ranking, in a standard way, is seemingly not likely given how subjective the difficulty of a code base is. This also completely elides the clever and best engineers that find ways to simplify and/or avoid solving problems entirely. Further, a team that built a crap pile of bad code, but know it pretty well could seem really productive just because they have built for themselves some job security. Then compound all this with measuring the utility of what was produced.