Analyzing Data to See Which Sport Really has the Most Parity: Part 2

Are there more statistics that show baseball is the most competetive sport?When you find data that suggests conventional wisdom may be false, it's always a good idea to do further statistical analysis rather than jumping to rash conclusions. It's true if you're doing Lean Six Sigma or, if you're like me, even when you're just talking about sports with your friends.

I've already used ANOVA to show that, contrary to common belief, the NFL may actually have the least amount of parity of any major professional sports league. Now I’ll use Minitab Statistical Software to look at the distribution of winning percentages for each franchise to see if there is more data to back up my allegation.
I took the average winning percentage of every NFL, MLB, NHL, and NBA team over the last 15 years and made histograms of the winning percentages for each league. Leagues with more parity will have a narrow histogram with a high bell curve. Leagues with less parity will have a wide histogram with a low bell curve.

Note: Because both teams are awarded points in an NHL overtime game, the average winning percentage for that league was not centered around 0.500. I adjusted the numbers so that it was centered around 0.500. Although this changed the winning percentages of each team, it did not change the distribution of winning percentages, which is what we want to compare.

Histogram of Winning Percentages

Look how high the curve is for MLB and the NHL. This means that over the last 15 years, most of their teams have winning percentages around 0.500. However, the winning percentages for the NBA and NFL are much wider. This means those leagues have fewer “average” franchises, and more teams that are consistently good and bad. Here are the five best and five worst franchises in each league over the last 15 years. 
Best and Worst Franchises

These statistics give us further evidence that baseball has the most parity and the NFL has the least. The Patriots, Colts, Packers, and Steelers all have better winning percentages over the last 15 years than the Yankees. The Lions, Browns, Texans, Cardinals, Bengals, and Raiders (not pictured) all have worse winning percentages over the last 15 years than the Royals. And look at the Atlanta Braves: They have the second best record in baseball over the last 15 years and haven’t won a single championship. That’s parity!

So the data analysis has told us that baseball has the most amount of parity, hockey has a little less, and football and basketball have the least amount of parity. So where did the conventional wisdom of the NFL having the most parity come from? There has to be some explanation...and there is. So far I’ve simply been looking at data from the regular season. Next, I'll look at what happens in the postseason.




Name: Jay • Tuesday, November 8, 2011

This doesn't show anything other than the fact that the sports have different typical ranges for results. You're not going to see a 20-142 team in baseball, but you can find 2-14 teams in football. So, naturally, the MLB data will be more centered around .500 as the range of results in any given season are more centered around .500 than any other league.

Name: Kevin Rudy • Friday, November 18, 2011

Keep in mind this is the average record of each team over the last 15 years. Yes, no baseball team is going to go 20-142. But if the NFL really has the most parity, shouldn't the football team that goes 2-14 get high draft picks, be able to improve, and at some point go 14-2 to offset their 2-14 season? Over the course of 15 years, a league with parity should have most of their teams even out to around .500. This is showing that’s not true for the NFL. Those teams that are 2-14 and 3-13 (Lions, Browns, Cardinals) continue to be bad year after year. And the teams that go 14-2 and 13-3 (Patriots, Colts, Packers) continue to be good year after year.

Name: McLain • Monday, May 27, 2013

The meaningfulness of parity is when considered within two contexts: first, the ability for asymmetrically-resourced teams to compete on even grounds. Secondly, the ability for asmmetrically-resourced teams to have mobility (to improve).

This analysis completely misses the point. The NFL is the king of parity because of the range of spend among those teams you're ranking. Pittsburgh, a small market, spent the least of any team in the NFL over the period where they had two championships. The hard salary base/cap and revenue sharing of the NFL (as well as smaller sample sizes in terms of the season and postseason, and a few other factors) makes it more easily possibly for relatively under-resourced teams to compete with the giants of the league.

Name: Kevin • Tuesday, May 28, 2013

I agree that the way the NFL is structured, it's set up to be a parity filled league. But when you look at the numbers, I don't believe it plays out like that. Sure, Pittsburgh can win as a small market team, but if it's so easy to improve why can't Cleveland or Detroit win? Despite all the money sharing and the small sample size, those two franchises have played in a total of 3 playoff games in the last 15 years (and lost all 3). And on the flip side, despite having a small payroll and being in a small market, the Royals would have won their division if the MLB season was 16 games this year!

But thanks for reading and for bringing in a different point of view!

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