def,
thanks for looking into this issue...
but i think your report pinpoints the problem...when a stock is 'in play' is exactly when many short traders start watching for an opportunity to short
what goes up must come down (not always, but it often works this way, especially for the past year)
your report also explains why many of them do become available later, when they are no longer in play, but when they also do not represent a short trading opportunity
As one good example, PCLN comes to mind: 1.7B mkt cap, 6M avg vol (3 month) and 100M float. PCLN reported 7/31 AC but was not available to short on 7/31. It is available today and, no, I don't know at what point it became available. When I checked the short list 7/31 and it was not there I moved on. But PCLN gapped on 8/1 and rose to @ 10.50 then dropped to @ 9.50 throughout the rest of that day. That move represents approximately a 10% gain for anyone who was able to short it.
Another thing that seems strange: PCLN was not available to short even BEFORE it moved up. I speculate that, like me, some traders anticipating a rise in price see this as a future (in a day or so) short opportunity. From the behaviour I have observed with PCLN and other stocks, it seems like somebody with clout (unlike me!) may somehow be reserving shares to short when the time is right. Is it possible for certain industry insiders to set aside shares, so that they are at their disposal to short if they so choose? You mention that IB uses borrow lists from other entities. Is it possible that somebody at one of these other entities is being stingy? I am simply trying to come up with some type of theory to explain these observations.
P.S. i am not down on IB, quite the contrary. things change fast, as we all know, and a more comprehensive shorting capability would be a positive change for IB. it would further enhance IB's philosophy of a 'level playing field'
IB traders are extremely lucky to have someone like def actually getting into the trenches, filtering through our complaints and our ideas, and making recommendations to IB decision makers. I believe that the Best_ECN routing was a result of this type of interaction.