Z, do you follow "retail only buy to open" P/C? Essentially it deals with small (less than 10 contracts) buy to open transactions. Reported weakly by OCC. Very few follow it and I don't think it is manipulated (as opposed to odd lot short sales, for example).
Right now it is 0.35. In the last four years it was at this level twice: Dec 2000 and January 2004, in both cases it was the top.