Bookmakers were quick to post spreads and totals for every 2021 NFL regular-season game, which allowed us to calculate market-implied power rankings. These give the most accurate representation of how oddsmakers currently rate each team, which allows bettors to easily see which teams the market overvalues and undervalues.
There are other less obvious benefits from this calculation, as it also allows us to evaluate broader trends in the betting market that are apparent at a league-wide level. Inspired by questions from NBC Sports EDGE Betting's Drew Dinsick and subsequent work by PFF's Lee Sharpe, I felt it worthwhile to answer some of the broader inquiries using the information available in the market-implied power rankings.
What is home-field advantage worth?
Home-field advantage was a hot-button topic heading into the 2020 coronavirus-impacted season, with most betting models needing manual intervention to help account for the unknown impacts. Most of the research up to this point has shown there is little actual home-field advantage found in NFL matchups, but it is something the betting market still adjusts for.
There has been a noticeable dropoff in impact on spreads, as the 2021 season shows .62 of a spread line that can be tied directly to home-field advantage. This is a significant change from the 2-3 points often cited as the number used by most models. Undervaluing home-field advantage looks to once again be a viable approach to betting again in 2021.
How much is a bye worth?
Bye weeks or rest differentials are often cited when evaluating matchups to bet during the middle stages of the NFL season. From the market-implied analysis, it seems that oddsmakers give significant weight to a team playing at home coming out of their bye. This has the added benefit of home-field advantage, as we see over a one-point line movement toward the home team after an off-week.