I believe they run test structures.
There is some data that is private and some that is communal.
I suspect some wafers are communal and some private and confidential.
Things like lithography metrics benefit from totalling everybodies' wafers.
@supersonic76, I was checking up on this. Indeed, I would think even 32 nm hp is not yet nailed down, given the serious LER (well exceeding 10%). That's why there has even been talk of EUV being used in double patterning context, like complementary lithography proposed by Intel. Of course, consideration of double patterning defeats purpose of considering EUV.