Thursday, October 16, 2014

Turnover Index - Week 7

Finally, a chance to lose some money. Week seven marks the first official appearance of the Turnover Index. The Turnover Index is a simple betting strategy based on the theory that the market overvalues defensive turnovers when judging team strength. See here and here for more background.

Driving the lack of betting opportunities is a lack of turnovers in general. Turnovers in the NFL have been declining for well over twenty years now. Through week six, teams have averaged just 1.5 turnovers per game, the lowest level going back to 1989. See chart below:


The full season results show the same pattern:


It is interesting that fumbles show a more steady decline than interceptions. With rule changes that have favored the passing game, I would have expected a bigger decline in interceptions, not fumbles.

Week 7 Picks

There are two picks against the spread this week: Jets to cover against the Patriots tonight, and the Steelers to cover against the Texans. We use the Kelly criterion to determine bet size. Here are the details (more background here):

turnovers
gameawayhomediffper gamepickprobbet
Jets @ Patriots 3 14 11 1.8 Jets 54.2% 3.8%
Texans @ Steelers 14 6 -8 -1.3 Steelers 53.0% 1.4%

So, for the first week, we will be wagering 5.2% of our bankroll.

2 comments:

  1. Sorry if I'm entering this twice...my first attempt seemingly didn't go thru.

    I tried to replicate the results you described in your original article on Turnover Index, particularly >=10 from 2005 to 2011. The ATS winning pct. was 58% instead of 61%. The query I used at KillerSport:

    tS(o:fumbles lost)+tS(o:interceptions)+10<=oS(o:fumbles lost)+oS(o:interceptions) and 2011>=season>=2005

    What did I do wrong?

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    Replies
    1. Nice query. I didn't even know you could do that. I excluded week 17 from my results in the original post (too much randomness in that last week). If I exclude week 17 in the query, I get 62.2% ATS. Not exact to my table, but pretty close.

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