With last Friday being the last trading day for 2013 effective status,
The funds that trade indexes had to rebalance their holdings.....
Win was removed from the growth index meaning selling took place leading up to Friday from when the changes were announced.
Win was added to the dividend index meaning buying after having previously sold off the growth index... some just traded one index to the other last Friday.
Trading of 10 percent of outstanding stock in one hour after hours sounds impressive but just year end rebalancing ..... JMHO