Pro-Football-Reference.com calculates the expected win-loss record for each team and lists it on the team page for each season. They explain:
this is an estimate of what the team’s record “should have been,” given the team’s points scored and allowed. The concept goes back to baseball analyst Bill James’ Pythagorean formula.
If you want to read the nitty-gritty details you can read the p-f-r.com blog post. The short version is that there is a correlation between team record and points scored and points allowed. Running the numbers for each team in the NFL in 2011 spits out what the historical data suggests the team’s record should have been.
While some teams will overachieve in regards to this mark with others falling short, the expected record is what should be expected from the point totals in the long term. In essence, we get a look at which teams benefited from random variation or “luck” and which weren’t as fortunate.
Here is a table showing the actual and expected win totals for each NFL team for the 2011 season. The column on the right displays the difference between the two with a positive number indicating a better than expected win total.
A natural question to ask is, so what? From the Lions perspective, we see that the Lions’ 10 win season can’t be construed as either lucky or unlucky. They put together a legit ten-win season and any regression or progress they make in 2011 will be a result of their actions rather than a return to the mean.
The Packers turn out to be the “luckiest” team in the NFL but still remain solid as an expected 12-win team. The Vikings and Dolphins each under-performed expectations by 2.5 games suggesting a multi-game improvement for next season could be built in as a starting point to this offseason.