It looks to me like someone has been playing with the shares to keep the PPS stable. They jumped in and manipulated whenever they detected that it was necessary to keep it below $48. Today (Friday) they didn't have to jump in.
WHY DO THEY WANT IT AT $48?
Day - - - - - - - - - - - - - - Volume - - - - - - - - Closing Price
Monday 30 January - - - 446,200 shares. Closing Price = 48.06
Tuesday 31 January - - - 983,700 shares. Closing Price = 47.83
Wednesday 1 February - - - 2,372,100. Closing Price = 47.76
Thursday 2 February - - - 488,800. Closing Price = 47.70
Friday 3 February - - - 155,351. Closing Price = 47.84
This has been going on since 22 December when the Volume was 1,850,600 and they knocked the PPS down from 49.92 to exactly $48.00