It’s not really intended to be retrospective like that. It’s predictive — it’s meant to temper what we might think about teams with certain records at a glance (OMG Atlanta 7-0!!) by heavily regressing those records to the mean. In other words, it tells us how much we really know about a team’s true quality from its W-L record. (The 2-year system from this post is just an extension of that theory, since Dave was curious.)

Continuing with the Falcons example, even being 7-0 (on the heels of a 10-6 season) doesn’t actually actually prove they’re anything more than a “true” 11-5 caliber team… Good, but not great. You’re not necessarily learning anything about the relative order of teams from this (although the 2-year version does a good job integrating last year’s performance into what we’ve learned so far this season), but you are learning about the relative talent levels of teams going forward. The spread of talent is nowhere near as wide as we might think it is from raw W-L records.