For the third-straight year, college football’s preseason Associated Press poll was headlined by — wait for it — Nick Saban’s mighty Alabama. The Crimson Tide usually deserve that honor, of course: They’ve won two of the four College Football Playoff championships, losing the title game on another occasion. But the Tide’s ubiquitous presence atop the rankings is also the most prominent sign that college football may have a parity problem. The sport’s most powerful teams are as entrenched as ever: Including Alabama, six of the top seven teams in the 2018 preseason poll have made the playoff at least once before, gobbling up 13 of the 16 total playoff slots available since the playoff began in 2014. College football has always been a plutocracy, but recently it has concentrated even more of its spoils among an even smaller group of schools.

We can see this trend playing out in a number of different ways. For one thing, it’s been harder for less-heralded teams to break into the top of the national rankings since the playoff began. Last December, I used a combination of the pre-bowl AP poll and our Elo ratings to reconstruct hypothetical College Football Playoff fields for seasons from 1988 to 2013, the year before the playoff officially began. Using that data, plus actual playoff picks for the seasons since, we can map out the chance that a team ranked at a certain level in the preseason poll would finish in playoff position by year’s end. And it’s clear that over the past four seasons, a greater share of highly ranked preseason favorites have made the playoff than would have over the preceding 25 years.

For example, before the playoff era, we estimate that about 53 percent of teams ranked in the AP’s preseason top five would eventually go on to finish in playoff position (according to our cocktail of Elo and the AP poll). Since the playoff began, though, 63 percent of the AP’s top-five teams have actually made the playoff. That trend holds for the majority of slots in the preseason poll, all the way down to the bottom — tellingly, no playoff entrant has ever ranked worse than 19th in the preseason poll. By comparison, we estimate that 7 percent of hypothetical playoff berths in the pre-playoff era would have gone to teams that started the season unranked.

In other words, the College Football Playoff is getting more exclusive — despite its supposed intentions to give more teams a chance to “prove it on the field” (rather than in a computer model). A greater share of playoff berths is going to the most talented teams than would have been the case in years past.

Now, maybe that’s an artifact of how teams are distributed in conferences nowadays, or how they choose to schedule their games. But even in terms of schedule-adjusted performance, the current top programs are finding it easier to maintain their elite status. For every four-year period since 1992, I looked at teams who ranked among the top quartile of the Football Bowl Subdivision (aka Division I-A) in our Elo ratings, tracking the rate at which they remained among the top quartile four seasons later. Early in that sample, a large share of top schools stayed in their lofty perch. For example, 63 percent of top-tier teams in 1994 were also among the top quartile in 1998. But for a brief stretch leading up to the playoff’s founding, that appeared to change: Only 43 percent of top-quartile teams from 2009 boasted the same classification in 2013, and the average (per four years) over the entire period from 2006/10 and 2009/13 was 47.5 percent.

That represented a rare stretch where top teams were more likely to fall out of the top quartile than stay in it. Since the playoff came into being, however, the trend has reversed itself: Roughly 68 percent of teams that were among the nation’s top quartile in 2013 also finished among the same group last season, the highest rate for any four-year period in our sample. It was hardly a fluke, either — aside from a couple of downward blips, the share of powerful teams retaining their strength four years later has been on the rise over the past decade.

As for why it’s happening, we can look for clues in which programs are getting the best talent. For each year from 2006 to 2018, I collected data on the top 25 schools in ESPN’s RecruitingNation class rankings and checked the correlation between a team’s recruiting ranking and where it had finished in the previous season’s end-of-year Elo ratings. And from the mid-2000s up until a few years ago, there was only a moderate relationship between a team’s existing level of performance and the quality of recruits it was hauling in. In other words, even teams coming off mediocre-to-poor seasons had some access to the sport’s top high school players.

But ever since the playoff era began, elite programs have begun exerting more influence on recruits than before. The correlation between Elo and recruiting power in 2015 (0.562) was the highest it had been in at least a decade. And although the top teams didn’t exactly steamroll lesser squads in 2016’s recruiting rankings, the correlation jumped back up in 2017 (0.573), and it skyrocketed even higher this year (0.681). At no point in recent history have teams that were already strong hauled in better talent than they are doing right now:

All of this helps add up to college football’s current period of hegemony under powerhouse programs like Alabama. Just to use the Tide as an example: They perennially snag the best talent (Bama hasn’t finished lower than sixth in ESPN’s recruiting rankings since 2007), then consistently turn that on-paper edge into results on the field. Saban’s crew would be great in any era, but it’s currently leading the charge in an environment where the best programs find it easier to stay great. That’s why we’d better get used to seeing the same teams muscle into the playoff year after year — and if you happen to root for a school outside that ruling class, well, good luck.