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Monday, October 29, 2007

Why Some Teams are Good, Part 2 - Population

Obviously, a team has a better chance of landing a recruit if he lives nearby (or, in the case of Joe McKnight, they might be wishing they had stayed closer to home). In this blog I provide some evidence to support a claim I made in part 1 that increasing population increased the talent pool and, therefore, led to better football teams.

I picked 8 states more or less at random. I tried to include states from a variety of regions, with a variety of sizes and that have experienced a variety of population trends. I have included both Nebraska and Oklahoma, and, honestly, I don't know why.

Ratings come from Soren Sorenson, who you will find listed in the Statistics Hall of Fame. I have added 5000 to all scores so that they are all positive (Sorenson's system ranges from -4000 to +4000, +or- a thousand). Population data is drawn from the Census. Census data is collected every ten years and I have used my own estimates to fill in the gaps.

I have looked at states as a whole, adding together the ratings of all teams in that state, because teams in the same state recruit for players in the same talent pool. For now, I am ignoring population growth in the region (e.g. Georgia benefits from population growth in Florida), and characteristics of the population (e.g. old people in Arizona don't play football), but some day I will look at those issues in more detail.

So, first we begin in 1950.

The 8 states are Nebraska and Oklahoma, which I already mentioned, Florida, Arizona, New York, Indiana, North Carolina and Alabama. The graphic on the left shows the teams as they were ranked in 1950, color coded by state. Florida State, UCF, USF, and Buffalo did not have D 1 programs at the time (or, in some cases, did not have a football team, or just started admitting boys to the school).

This chart is important because, from here on, I will be focusing on indexed values for the state, so that indexed value will always reference back to this starting point. For example, 1950 was a good year for Oklahoma and Army (perhaps the two best teams in the country). This will be important to keep in mind.

This next chart demonstrates an important principle as well. This compares the percent of the total points held by a state (with their scores added together) of all the points available against the percent of the US population in that state. So, New York, despite Army's success, was under-performing. Anyone who has been to a high school football game in Dallas and in Rochester knows why this is happening. It shouldn't surprise anyone that Oklahoma performed the best giving their population size. Alabama was facing a unique challenge in segregation. It would be another 20 years before Sam Bam Cunningham would convince Bear Bryant to integrate, allowing Alabama to dip much deeper in its talent pool.

The population of most states would grew over the next 50 years, but some grew much faster than others. Florida and Arizona are good examples of states that blew up in terms of population, while New York stagnated.

In the following charts, I present data for each state in terms of their performance and their population over the 5 decades from 1950 to 2000. The black line is the team's performance. It is a running four year average which I use under the assumption that players from a cohort will play for a team for four years. The red line is the indexed population, where 100 is equal to the population in 1950. The blue line is based on the same principle, but represents the percent of the US population represented by that state, so that if a team's population is growing slower, but slower than the entire US, the blue line will fall but the red line will rise. The red line, therefore, represents the real talent pool and the blue line the relative talent pool, and because teams are good relative to each other, we should focus on the blue line. (You can click the charts to see a bigger version.)

Nebraska had some kicking teams in the 70's and the mid to late 90's, which shows up in their chart. The population as a percent of the US population was actually going down, but Nebraska kept spitting out world class teams. It makes me think that Osborne may have been a much better coach than we give him credit for. Arizona's performance isn't improving with its rapidly growing population. I think two things are at issue. First, Arizona doesn't have as strong of a football culture as the rest of the South and, second, Arizona's programs might be experiencing a bit of a lag.

I was a little surprised to see how well Indiana fits the pattern. Notre Dame has a unique advantage to recruit nationally and should be able to overcome general demographic shifts. Notre Dame claims their challenges are rooted in high academic standards, so I guess I'll have to look at that claim another day.

Alabama has been generally outplaying its population since the 50's but, like all the others, its performance is generally falling with the decline in its relative population size. The effect of integration on performance is still a little unclear, but something I will definitely look at more closely in the future.

But the overall results from this little experiment are clear--population trends in a region definitely effect the performance of that regions teams. The black lines tend to go where ever the blue lines are going. It also shows that we can't ignore culture, quality of coaches and the power of programs to attract players from long distances.

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