Consensus on this seems to be ZDR which tracks to my own experience as well. If that really turns out to be the case, it's an incredibly strong and clear message to the labs on the impact of data retention policies.
Lots of folks jumping to conclusions on the FT market share data for Fable. The reason is not at all obvious to me. Is it due to cost? Speed? Aggressive moves from OAI? ZDR? Open Source? Bad press / vibes? Refusal to work in some domains? Biased data?