redsox2009,
I think the figures suggest it is mainly due to retrogression of the EB2 dates.
Receipts
Month -- NSC/TSC -- India ------ WW
Oct11 -- 17,562 -- 15JUL07 -- Current
Nov11 -- 20,977 -- 01NOV07 -- Current
Dec11 -- 23,708 -- 15MAR08 -- Current
Jan11 -- 27,506 -- 01JAN09 -- Current
Feb12 -- 30,551 -- 01JAN10 -- Current
Mar12 -- 26,717 -- 01MAY10 -- Current
Apr12 -- 18,341 -- 01MAY10 -- Current
May12 -- 15,802 -- 15AUG07 -- Current
Jun12 -- 17,170 -- UNAVAIL -- Current
Jul12 -- 15,560 -- UNAVAIL -- 01JAN09
Aug12 -- 12,657 -- UNAVAIL -- 01JAN09
Sep12 -- 10,826 -- UNAVAIL -- 01JAN09