The S&P 500 does this for stocks; perhaps their implementation and design choices can find some application here?
Regardless, we think stock indexes are indeed are good role model for this kind of exercise. If there's interest in this we might invest in: (a) continuing to track this with better documentation on how we do it, and (b) start tracking more categories of parts.
Kinda pedantic remark:
No longer relevant as a stand-alone device but don't overlook the IP core market. It's pretty common to find one or more of these old cores as a module in a more complex device (e.g. an FPGA) or as the base for an ASIC (esp. automotive). Same for the 8088, 8051, 6502, ...
But regarding those old cores I mentioned ... lots of use because it's legacy with lots of developers that know the architecture.