The 2014 Major League Baseball regular season is over, making it the perfect time to look back at how stat pundits performed at predicting each team’s total wins.
Last year, Trading Bases bested competitors while also outperforming totals set in Las Vegas.
Before looking at this year’s results, let’s take a look at our competitors, along with each ones’ abbreviations.
O/U: The over/under set for each team in sportsbooks. I used ones set by sportsbetting.ag in early March (Note: if you are scoring at home, all bets I extracted were between +115 and -135. For simplicity, I treat each the same way)
BP: Baseball prospectus (PECOTA). Picks were taken from the site before the season, although there does not appear to be an active link for these projections.
PM: Prediction Machine
FG: Fan Graphs. There does not appear to be an active link for these projections, although the AL West’s are here
TB: Trading bases, the 2013 winner, and a website of Joe Peta
DP: Clay Davenport
Ensemble: An average of the first four site’s above.
Here are my metrics
MSE: Averaged squared error between the prediction and the win totals (lower is better)
MAE: Averaged absolute error between the prediction and the win totals (lower is better)
Percent: Fraction of successful over or under bets (higher is better)
While Fan Graphs and Davenport appeared to outperform its competitors and boasted slightly lower average errors (MSE, MAE) than sportsbooks, betting each team according to both Fan Graph’s and Davenport predicted totals would have finished just 13-17. In general, the number predicted by sportsbooks finished closer to the eventual win totals.
In summary, it’s pretty amazing that not a single one of the nine prediction methods I used was able to finish with an overall record above 0.500.
Lastly, I plotted the predicted and observed win totals, using both sportsbook predictions (abbreviated as “Las Vegas Prediction”) and the ensemble method (the average of the first four sabermetrics/statistics sites above, listed as “Steadheads Prediction.”)
Win totals were relatively accurate for most teams. The Rockies, Diamondbacks, Rangers, and Red Sox all falling short of expectation, while the Marlins, Orioles, and Angels all outperformed expectations.
Interestingly, betting the “over” on the 15 teams with the lowest predictions, and the “under” on the 15 teams with the highest prediction would have finished 19-11.
Thanks for reading, and if you have any other prediction website’s you’d like me to include, feel free to send them along.