The recruiting rankings, which are led by the Composite rating service, are likely evolving their analytical techniques. If this is true, then there should be some identifiable changes in output over time. I took a look at the top 1000 recruits from 2005 through 2020 and averaged their ratings. I then standardized the ratings to see if any significant movement is occurring over time.
The above chart shows the raw scores for each year. It is easy to see there was a fairly sharp upward trend in average ratings from 2005 to 2009. From there, it looks like things have leveled off for the most part.
When I standardized the scores, we can see just how sharp the rise was. It also looks like things have generally trended upward since 2017. Because there is some rise, it may be wise to take the baseline changes into considerations when comparing classes over time. That being said, the effect does not look to be too dramatic.
The above table shows the raw and standardized scores. The numbers in the bright green boxes are the group average and standard deviations. All in all, the top 1000 average out fairly consistently, though there is definitely an overall upward trend.
When we look at this more deeply and parse out by positions, the trends stay the same.
In this table, we can easily see that with the exception of center and fullback, all position groups are trending toward higher average ratings since 2009. Something must’ve happened in 2009 that lead to a change in how recruits were rated. Every look so far at the data shows a sharp climb from that point on. In looking at the positions combined into position groups, we see the trend continue.
The table below shows the average rating for top 1000 recruits by position group. The offensive skill group consists of QB, RB, APB, WR, and TE. The others are self-explanatory.
When we standardize these scores and apply heat-mapping, the contrast is again clear- from 2009 on there was a sharp rise.
Since there was a clear delineation in ratings from 2009 on, I charted the data without years prior to that. There’s a bit of variance in that time. 2018 and 2019 were both pretty high above average for the group, and 2011 far below. So far 2020 appears to be reverting to the mean.
The key takeaway is that when comparing class ratings over time, it might be a good idea to control for rating inflation. This is easy to do by simply standardizing each year’s data and moving forward with standardized values rather than raw values.