Although not a direct answer to your question, this month's CX World states that the PER route has been the most popular to attract bids. I'm not sure if this means successful bids, or just number of people actually doing bids.
Interesting, sitting here having just completed LHR/HKG/PER. Wasn't eligible to bid, but got an OPUP from PE to J at the gate at HKG, as did my neighbour from the LHR leg.
Maybe there is something in the speculation that bids to upgrade to PE are causing OPUPs out of PE.
Just an idle thought from a happy punter.