Curse Of The Billy Goat

October became a little greener on the final day of the regular MLB season with both the Los Angeles Dodgers (~1.29) and the Pittsburgh Pirates (~1.48) both winning. That makes it seven from seven for this season and over five years since the last sub 1.51 hot favourite lost an October regular season game.

The third profitable season in four, and the record of this strategy over the last twelve seasons looks like this:

Over the twelve seasons, the strategy is most profitable in April (+22.55) and least profitable in September (-64.90) but clearly things have changed and the conclusion of a famous study from 1994, updated in 2003, doesn't seem to hold true today*.

In contrast to the consistently observed favourite–longshot bias found in racetrack betting markets, it has been shown that gamblers in the market for Major League Baseball games reveal the opposite behaviour. This paper updates the previous study with ten years of additional data for the 1990–99 seasons. The strength of the reverse favourite–longshot bias is virtually identical to the original paper. The result suggests that, contrary to most reported inefficiencies in gambling markets, this bias appears to be permanent.

Permanent? Never say never. The strategy is profitable from as far back as 2008, with the most recent eight seasons +34.06. Since the 2007 season, every month with a full schedule is profitable bar May, which strangely was the most profitable month when the reverse  favourite–longshot bias was, while waning, still present.

It's also interesting that fewer teams, a lot fewer in fact, have been starting at 1.5 or less in the last few seasons. The 356 in 2004 became just 124 ten years later. Baseball punters becoming a little sharper?

Anyway,regular season is in the books now, and by the time the new season rolls around next April 4th you'll have all forgotten this, so it's on to the play-offs which start tonight with the New York Yankees visiting Houston for a one game play-off. The Astros are slight favourites, and the following evening the National League's Wild-Card play-off game sees the Chicago Cubs favourites to win in Pittsburgh.

While laying all favourites has been profitable in the play-offs since at least 2004, (only in 2009 would more than a small loss have been the outcome), laying away favourites has been more profitable than  home:

Should the strategy prove successful in Pittsburgh on Wednesday night, it will of course mean the Curse of the Billy Goat will continue for at least another year. It's only been 107 years - what's another one?

* Another study noted that:

Woodland and Woodland (1994) argued that betting in baseball yielded a reverse favorite-underdog bias, with underdogs underbet. Gandar et al. (2002) made a minor correction to the Woodland-Woodland methodology and found that if there were any bias, it was very slight.