Over the past few weeks (and especially after the beatdown that New England laid upon the Titans) I've been hearing commentators, colleagues, and friends claim the NFL just isn't very interesting this year. The claim is that the competitive balance of the league, or the evenness between the teams, has taken a huge downturn and there must be something wrong with the league's construction. My first thought is that the NFL has long been generally thought of as the most balanced league of North America's Big 4 and any change it would see would most likely be downward (when you're at a peak, the only way to go is down). My second thought was that, yes, there do seem to be a large number of blowouts this season. But looking at the standings, I just don't see that clearly. There are only 4 teams with more than 6 wins thus far in the season, and yesterday the awful Redskins beat the not-so-long-ago-unbeaten Denver Broncos.
Now that we're at a point where everyone has played 9 games (except for the Browns and Ravens tonight, but for the sake of saying this year is unbalanced, I'm assuming the Ravens win) I decided I'd check to see if there has been a significant change in balance this season. I'll just use a simple Ratio of Standard Deviations (RSD--a measure popularized by Roger Noll and Gerald Scully). This measure is a ratio of the standard deviation of winning percentages (SD) divided by the "idealized" standard deviation in a perfectly balanced league (ISD). A perfectly balanced league is defined (as all teams having a record of 0.500)--this is a stupid mistake on my part as noted in the addendum below...especially since I work with this data a lot. The reason for the denominator is to control for the number of teams and number of games played in each season to make it comparable across sports or seasons in which these variables change. The lower the RSD, the better the balance. From 2001 to 2008, the RSD was as follows:
And at the 9-game point in the 2009 season, we see: 1.448
So, at this point in the season, it looks as though we're on the better end of the balance spectrum (if you believe that more balanced means a better league--which, of course, is always up for debate). Keep in mind that RSD is not the only way to measure balance. However, it works as an interesting quick check on the distribution of wins around the league. It very well could be that there is a huge gap in talent between the top and bottom teams, where the best teams pummel the worst. We've seen some of this, but we've also seen the Redskins beat the Broncos and the Raiders beat the Eagles.
To be honest, I enjoy a demolition every now and then. Watching the spectacle of Tom Brady throwing 6 TD passes in one quarter is a lot of fun for me. It would probably get boring if there weren't teams that could challenge the Pats, Colts and Saints, but I don't think there's any lack of competition in the NFL as the Saints last few games have shown. I'm not ready to conclude that the NFL system is now completely broken, so let's not rush to fix it.
ADDENDUM: Guy points out a problem with my explanation. The ideal league isn't one with all .500 teams, but one where each team has a 50% chance of beating any other team. He makes some points about the difficulty at the extremes for balance, which are good to keep in mind. The correction for the model in terms of season length can overcorrect for short seasons like 9 games, making the RSD look more balanced than the league actually is. Given this, I still don't think balance is a hugely significant problem in the NFL this season as some commentators have tried to point out.
Thanks to http://www.rodneyfort.com/ for the data on past NFL season RSD. You can find the data for this post, as well as numerous other sports business data files by clicking the link on the sidebar.