NFL: A weird thing about tie games

Starting with the 1974 season, the NFL has had sudden-death overtime for regular season games. A very interesting statistic emerges if ties are categorized as either 'early season' (weeks 1-8) and 'late season' (week 9 on).

Late Season Ties

Late season ties are pretty rare, but seem to happen fairly consistently at about once every five seasons:

1. 1978 Week 13: Vikings 10, Packers 10
2. 1984 Week 10: Eagles 23, Lions 23
3. 1989 Week 11: Chiefs 10, Browns 10
4. 1997 Week 12: Eagles 10, Ravens 10
5. 1997 Week 13: Giants 7, Redskins 7
6. 2002 Week 10: Falcons 34, Steelers 34
7. 2008 Week 11: Eagles 13, Bengals 13

That's 7 late season ties over 35 seasons which gives an average of 0.2 ties per season, or one every five.

Early Season Ties

From 1974 to 1988 (15 seasons), there were 9 early season ties:

1. 1974 Week 2: Steelers 35, Broncos 35
2. 1976 Week 2: Rams 10, Vikings 10
3. 1980 Week 6: Packers 14, Buccaneers 14
4. 1981 Week 5: Jets 28, Dolphins 28
5. 1982 Week 7: Packers 20, Colts 20
6. 1983 Week 8: Giants 20, Cardinals 20
7. 1986 Week 7: 49ers 10, Falcons 10
8. 1987 Week 2: Broncos 17, Packers 17
9. 1988 Week 5: Chiefs 17, Jets 17

From 1989 to present, there have been no early-season ties. None.

What Happened Since 1988?

... that's a good question, with no obvious answer. There's no obvious commonalities in the teams that had early season ties. They range from the very bad (the 82 Colts finished 0-8-1) to the very good (the 74 Steelers finished 10-3-1, and went on to win the Super Bowl). There are games featuring two weak teams (in 1980, the Packers and Buccaneers both finished 5-10-1) and two good teams (in 1976, the Rams and Vikings both won their respective divisions, and the Vikings advanced to the Super Bowl (losing, of course, to the Raiders)).

There were to major changes to the NFL that took place around 1988: the establishment of Free Agency starting in 1989, and the expansion to a 12-team playoff format for the 1990 season. Perhaps the expanded playoff field meant that teams were more likely to play for a win early in the season?