To second approximation, however, increasing the number of publications does not necessarily also lead to more good science. Two short papers don’t fit as much research as do two long ones. Thus, to second approximation we could take into account the length of papers. Then again, the length of a paper is only meaningful if it’s published in a journal that has a policy of cutting superfluous content. Hence, you have to further refine the measure. And so on.
This type of refinement isn’t specific to science. You can see in many other areas of our lives that, as time passes, the means to reach desired goals must be more carefully defined to make sure they still lead where we want to go.
Take sports as example. As new technologies arise, the Olympic committee has added many additional criteria on what shoes or clothes athletes are admitted to wear, which drugs make for an unfair advantage, and they’ve had to rethink what distinguishes a man from a woman.
Or tax laws. The Bible left it at “When the crop comes in, give a fifth of it to Pharaoh.” Today we have books full of ifs and thens and whatnots so incomprehensible I suspect it’s no coincidence suicide rates peak during tax season.