Wednesday, October 23, 2013

Turnover Index - Week 8

Here are the Turnover Index picks for Week 8. 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.

Week 7 results

Week 7 picks went 3-0 against the spread. Here are the season to date results:
  • Against the Spread: 4-2
  • Starting Bankroll: $1,000
  • Current Bankroll: $879 (-12% ROI)
Here is the week by week performance:

amount betprofitsending
4 2 0 $1,000 $268 (26.8%) ($268) $731
6 1 1 $731 $32 (4.5%) $29 $761
7 3 3 $761 $130 (17.1%) $118 $879

Were it not for my pathological honesty, I would be reporting a 4-0 record against the spread this season, as the the initial two losses in week 4 occurred before I could start publishing the turnover index this season. As I was running the data for this season's version of the index, I debated whether to start betting in week 4 or week 5. But week 4 showed positive returns over the testing window (1999-2012), so I included it.

Despite the positive 4-2 record against the spread, my bankroll (managed according to the Kelly Criterion) is still underwater, having lost 121 of my starting 1000 (Zimbabwean) dollars.

Week 8 Picks

There are three recommended bets against the spread this week: Falcons over Cardinals, Browns over Chiefs, and Jaguars over 49ers. The table below shows the turnover differential, probability of covering, and the recommended fraction of bankroll to bet, according to the Kelly Criterion. We're betting just 8.1% of our (fictional) $879 bankroll this week.

gameawayhomediffper gamepickprobbet
Falcons @ Cardinals 5 15 10 1.3 Falcons 53.7% 2.8%
Browns @ Chiefs 9 19 10 1.4 Browns 54.0% 3.5%
Fortyniners @ Jaguars 15 7 -8 -1.1 Jaguars 53.2% 1.8%

The "Old" Index

Under last season's simpler betting approach (bet any game with at least a 10 turnover differential), season to date results for 2013 are 2-1 against the spread.


  1. Full kelly betting is pretty aggressive. At least in the blackjack world, people tend to wager fractional, rather than full kelly in an attempt to reduce risk of ruin.

    1. True. And if I was managing a non-fictional bankroll, I would probably apply some sort of fractional approach. But since this is for illustration purposes, I didn't feel like adding another parameter to the mix (this "simple" betting strategy is already getting a bit too complex as it is).