(Click Graph to Enlarge) This is the third part of a four-part series in which I will try to compare parity in NBA, NFL, and MLB. The proxy for parity in this series will be “the ability of the cellar-dwellers to improve next year”.
I won’t concentrate as much on the year-to-year improvement as I will on the 5-year average because the 5-year average is a more stable and shows a trend. To create this chart I looked at the worst 5 teams in the league for each season from 1980 to 2009 and calculated the average improvement of those teams in the following season. For example, in 2003 season the worst 5 teams improved by an average of 3 games from the previous season.
The graph shows that the teams’ ability to improve increased slightly,
but steadily, from 1989 to 1995 and then from 1998-2003.
Overall, the NFL’s Upward Mobility has remained steady over the last 30 years.
That may be a tribute to the parity of the NFL, or the quality of the product, or both.
I can’t really figure out why and the aforementioned increases may just be by chance, as I did not do any hypothesis testing.
A stat that highlights my uncertainty about the causes and significance of the increases is:
The worst year for improvement was 2009 and the best was 2010.
I can’t explain that, can you?