Ann: Appendix 3B - Loyalty Option Conversions, page-3

I think you will find that the selling from loyalty options don't necessarily coincide with these announcements. For example, if you held some shares and you knew you were going to get 100 shares from exercising your options, you could sell 100 much earlier when you thought the SP was higher, then you could exercise your options later to get them back.
To get a better idea of how much more selling could come from the options, you'd probably have to total up the sell volumes on all those high volume days when we went really down. Does it total roughly 1/4 of total shares in circulation?