Vegas and the Fans

Vegas odds principally aim to achieve equal bettor action on over/unders. That is, the oddsmakers set the lines so that they can best achieve a 50/50 split on the bets. Their general aim is then to predict what the average gambling public will think about the number of wins a given team will achieve.

The fan projections here at FanGraphs, converted into wins by David Appelman, measures much the same goal except that the input comes from what is most likely a more forward-thinking and baseball-educated crowd and appeals to the same people.

These similar goals presents a great comparison opportunity. Here are some of the more egregious differences between the Vegas oddsmakers and the FanGraphs readership with CHONE’s projections provided as well.

Arizona. Vegas: 82.5, Fans: 87 (CHONE: 79)
Baltimore. Vegas: 73.5, Fans: 78 (75)
Cubs. Vegas: 82.5, Fans: 78 (79)
Angels. Vegas: 84.5, Fans: 80 (81)
Athletics. Vegas: 77.5, Fans: 81 (81)

Phillies. Vegas: 92.5, Fans: 84 (87)
Padres. Vegas: 69.5, Fans: 79 (78)

The first five teams listed all had about a 4-win difference between the fans and Vegas with CHONE mostly siding with the fans, aside from Arizona, and waffling between the two on Baltimore. The bottom two represented the largest divergence between Vegas and FanGraphs readers and, again, CHONE mostly agrees with the fans.

Is there a common thread running through the five teams where the fans and CHONE offer different opinions than the Vegas oddsmakers? I would say the general public, and Vegas by extension, are too prone to be swayed by 2009 results. Hence, teams that were good Angels, Phillies) or bad (San Diego, Oakland) suffer from some residual effects. The Cubs are present I expect because of their large and devotedly optimistic fan base.

In the end, I would consider shorting the Phillies, Angels and Cubs and buying on the Padres and Athletics.

Hat tip to Jonah Keri for passing along the odds.