Rolling Team Ratings
Play around with NBA history from 1983-84 to 2016-17:
If you need a refresher on team rating, it’s a metric that averages era-adjusted offensive and defensive scores, such that a team rating of exactly 100 indicates that a squad was perfectly average—whether by being perfectly average on both ends or by being as bad on one as it was good on the other. Here, we’re using a 20-game rolling version of team rating, such that every score seen is a weighted average of the marks earned during the game on that date and the 19 prior to it.
Only regular-season contests are counted, and there can be overlap between campaigns—but only at the beginning before a 20-game sample from the new season takes over.
Additionally, we’re adjusting the team rating earned during any given game by accounting for the strength of the opponent. Playing against a squad that finished the relevant season with a 105 team rating would yield a 1.05 multiplier, while working against an outfit that finished the year with a 95 team rating would lead to a 0.95 multiplier.
Essentially, if the San Antonio Spurs earn a team rating of 110 during two different games, one against an opponent with a 105 team rating on the year and another versus someone with a 95 team rating, their respective inputs for the contest in question would be 115.5 and 104.5. This way, it’s possible to have a below-average score in a narrow win against a weak foe, and it’s similarly feasible to earn an above-average score during a close loss to a superior opponent.