Yes, the rating system has not changed but the numbers being inputted into that rating system have changed significantly. In the other thread, someone pointed out that 13 of the 15 all time passer rating leaders are active players. Are the QBs today that much better than all of the other QBs in NFL history? I doubt it.
In 1996, Favre had 39 TDs, 13 INTs, 3900 yards and a 95.8 rating.
In 2009, Favre has a 107.2 rating. Even if everyone accepts that Favre was better in 2009 than 1996, is he really 11+ rating points better than he was in 1996??? He would be ranked the 10th best QB according to QB rating in 2009 with the 1996 numbers.
In 1997, in a league that had Marino, Young, Elway, Aikman, Favre, Moon, etc. Favre was 2nd in the league with 3,800 yards. In 2009, 1997 Favre would be 11th (just barely in front of Kyle Orten). Thats nuts.
There is clearly something going on with QBs ratings, yards, etc.