This is part two of a two-part series examining conferences in the NCAA tournament. Part one is here.
In part one, we examined the historical performance of college basketball conferences in the NCAA tournament. However, many of these conferences have changed significantly over the years. In part two, we will attempt to examine this topic in greater detail.
Simple Wins Per Year vs. Current Team Wins Per Year
To measure the effects of conference re-alignment, I compared two simple metrics. The first is the original Wins Per Year metric, as seen in part one, which measures the average number of wins each conference accumulated each year. The second metric, Current Teams Wins Per Year, is the total tournament wins produced by the current schools in the conference since 1985, divided by 31 (the number of tournaments since 1985). This comparison shows the shift in teams over time, by comparing where they were when they won games in the tournament, to where they are currently.
Power Conference Wins Per Year
As we might expect, most power conference teams are winners by this measure. We see that the ACC, already the leader in wins per year, is only getting stronger after adding tournament regulars Syracuse, Pittsburgh, and Louisville to their roster. Meanwhile, the Big East took the biggest hit, losing about 40% of its yearly wins. Overall, four of seven conferences have higher CTWPY than their original WPY.
Mid-Major Wins Per Year
Where did all those wins come from? Well, these power conferences raided the best teams from the Mid-Major ranks. We can see that most of the Mid-Major teams have lost yearly wins, with Conference USA and the WAC being hit the hardest. Conference USA has lost about 60% of its yearly wins, while the poor WAC has been almost wiped out, losing 93% of its yearly wins.
Single Bid Conferences Wins Per Year
But things look even worse for the single bid leagues. From part one, we identified the Colonial and the Horizon as the single-bid conferences that most exceeded expectations based on their seeds. However, both have been crippled by re-alignment, losing most of their yearly wins. In fact, of the six single bid leagues who have historically produced more than 0.25 wins per year, five have lost more than 60% of their yearly wins. Only the MAC has been able to maintain their lineup of successful tournament teams.
While these metrics give a good sense of how modern conferences differ, one shortcoming is that they fail to account for the changes in size for each of the conferences. For example, is the ACC getting better, or just bigger?
A Measure of Conference Quality
To examine this idea, I used tournament wins since 1985 as a proxy for team strength. Using this metric, we can look at the average tournament wins per team in each conference as a measure of conference strength.
As we can see, the ACC is still the top dog. The average ACC has won just under 27 tournament games since 1985. The Big 12 and Big Ten are roughly even for second place, with about 21 tournament wins per team in these conferences. Rounding out the top seven are the SEC at about 18 wins/team, the Big East at just under 17 wins/team, the Pac-12 at 15 wins/team, and The American at 13 wins/team.
There is a large drop off after the power conferences, with 8.5 wins separating the average team from The American from the average Atlantic 10 team. We also see that the WAC, classified as a Mid-Major based on bids per year, has clearly fallen to the level of a Single Bid conference.
Conference Quality Over Time
Finally, we take a look at how this measure of conference strength has changed over time.
For most of the power conferences, we see a downward trend in wins per team. This suggests that the growth of the power conferences is diluting the quality of the average team in the conference. Indeed, only the Big 12 has increased its average wins per team, and it is also the only power conference that has decreased in size.
When we look at conferences outside the top seven, we see the toll that re-alignment has taken on them. This is especially true over the last five years, as we see a large drop in almost every conference sometime between 2011 and 2014. Conference USA, once just short of a power conference itself, has been completely picked dry, falling from almost 13 wins per team in 1996 to slightly over two wins per team now. The Horizon and the WAC have seen similar levels of destruction, falling from peaks of a healthy 9.4 (Horizon) and 5.6 (WAC) wins per team, down to 1.2 and 0.3 wins per team in 2016, respectively.
In the first section of this article, we saw that the Mountain West improved by the Wins Per Year metric, but it appears that improvement was due to growth in size, not quality. Its average team currently has almost exactly half the number of tournament wins as the teams that founded the conference in 2000.
Overall, we see a downward trend in this metric across all categories of conferences. The shifting of teams in the top conferences has a trickle-down effect that hurts everybody. The power conferences are absorbing the best Mid-Major teams, diluting their own product in the process. The Mid-Majors are losing their best teams, and replacing them with weaker teams from Single Bid leagues.
While this year has been celebrated as a year of parity, this data suggests that as conferences shift, this parity is more likely to be confined within the best conferences, as opposed to parity between power conference and non-power conference teams.
Data from Sports Reference College Basketball
Data organized and compiled using MySQL
Visualizations made with Tableau Public.