Professional Football Researchers Association Forum

ro football historians  must classify time periods as they analyze their sport.  The game has changed drastically both in the number of team and rules.  It going to be difficult to make any comparisons.  The major changes occurred after 1973 and again after 1993.  Between these years, there were also changes,  less numerous but very critical.


After 1993,
--Kickoffs went from the 40 to the 35 yard line.  If the kick went out of bounds the receiving team could take the ball at that place or make the other team rekick five yards further back;

--On punts, only the two ends could go down field prior to the kick; 

--Big change on field goals.  Assuming the defensive player never controlled the ball, missed field goals came back to the line of scrimmage.  If inside the 20, it was a touchback and the ball came to 20.  Prior this the NFL treated field goals just like punts.  The other team took over were the ball stopped or at the 20 if it was in the end zone;      

--offensive holding became ten yards from the line of scrimmage.  Prior to this, it was 15 yards from the spot of the foul.  This prevented allot of long yardage downs.  However, offensive holding is a safety if done in the end zone.

--to avoid a sack, a quarterback could throw ball away provided he it outside  of the hash marks, the ball was beyond the line of scrimmage, and or/and an eligible receiver was close.  Sacks became harder to get.   The new intentional grounding  was still 15 yards, plus loss of down or a safety if in the end zone..   This may only be a five yard penalty.  I am not certain.

After 1994,

--Kickoff were moved from the 35 to the 30.  If the ball went out of bounds, the offense took over at the 40 yard line; if outside of the 40 the offense takes it at that point.

--On missed field goal, the offensive team takes over at the point of the field goal, costing the kicking team another seven yards; if inside the 20, it becomes a touchback.  The offense takes the ball at the 20.

The first set of bullets is obviously after 1973 season, not 1993.

I think there was another major change you didn't include, which is the movement of the goalposts to the end line. The extra-point accuracy percentage cratered after that, even going below 90%, and didn't fully recover until 1994, the same year that the 2-point conversion was introduced. Here's a graphic I created in 2015 and haven't gotten around to updating since.



Not only did the movement of the goalposts affect extra points, but of course it meant that teams had to get 10 yards closer before kicking. I would also argue that it was one of the factors that increased the number of touchdowns, because a large obstruction was now removed from the goal line.