Thursday, 22 September 2011

Goal Mine

Does nobody study my spreadsheets? An audit of my XX Draw results uncovered a serious discrepancy, which cost me six point in profits, yet nobody noticed! The error has been corrected in the latest update, which combined with the two losers in Italy last night, drops the ROI on the season to just 4.83%. Not too shabby after a few hundred bets perhaps, but after just 30, nothing to write home about. Not that there would be any point, because hardly anyone in my family understands anything I write about in this blog. My son does, and possibly a nephew, but that's about it. A few games tonight, but a summary of midweek so far appears to be a loss in France (Bonnie Tyler anyone?), a matching profit in Italy, and a small profit in Spain. I'll update the final totals after tonight's games, and publish them, but for now these are close enough:

With over 300 bets already this season, it won't be too long before I have over 1,000 bets, and the ROI will start to be meaningful. Right now, it's up and down like a whore's drawers, but as George said in a comment on Monday,
"If you can support a 5% ROI edge over 1500+ bets, you are sitting on a gold mine, my friend..."
My own gold mine would be nice, but while there's a long way to go I suspect, the 'prospect' is exciting.
To address some of the other points raised by George, here are his comments:
Very useful to see your season-to-date stats. Lots of blogs focus only on the latest round of matches. Signal/Noise is so low that even a decent edge (pos or neg) is not obvious unless you have a large number of bets to study (250 is my rule of thumb). In your season-to-date stats, assuming zero edge, your results are 82nd percentile. Can't make it into an academic journal article, but practically very very good. What do your 10/11 season stats look like?
The value system only started late in the season for 2010-11, a trial in the EPL to iron out any spreadsheet issues, and while they were very profitable (Match Odds +12.9 from 26 bets. Over/Under +7.75 from 14 bets) I'm not going to include them in the running totals. Far too small a sample. George's second comment:
At what point in time and over how many bookmakers do you select the odds that go into your records? I have a bit of a problem with FE on this issue. If the target is good replication of the tipped bets, then a tipster (I am not saying you are one) should limit himself/herself to 4-5 big-limit, big-payback bookies (perhaps review them annually). Otherwise, there is a bias there, which in reality wipes out a significant part of the perceived/reported edge. Or one can simply report different edges for different contexts e.g. early-market (low-limit) edge, pinnacle-only edge etc. By edge, I always mean ROI%.
There is nothing sophisticated about the odds I enter - quite simply they are those that are readily available on Betfair. (Occasionally if the spread is 2.12 - 2.18, I will enter 2.15, if it is 2.12 - 2.14, I use the 2.12 as the back price although I will look for the 2.14 when I place my bet). I use the Betfair prices for two reasons - 1) Since a number of selections are Lay bets, this obviously limits my options to the exchanges and while occasionally BETDAQ may be a tick higher, it's not often and 2) I have no problem getting my bets accepted on Betfair whereas bookies would be a different matter. The prices entered are those at the time I happen to pull them, usually a couple of days before the matches, but occasionally closer to kick-off, for example weeks like this one where there are midweek games. For the Over / Under markets, prices can be a little soft if I try to pull them too early. George (the Third):
Why are you not looking at the Asian Handicap markets? As far as I am concerned, if there is liquidity there, I will dig for an edge. Asian handicaps is where the liquidity is. I think I saw something from you about the mismatch of incentives of teams on spread/handicap markets, which you don't like. Don't see how that's relevant. If your system finds value, then obviously it overcomes the incentives problem. If one cannot find value, then yes, the funny incentives could be used as a reason for not digging further, I guess.
I do not find much liquidity in the Asian Handicap markets, at least not those on Betfair or BETDAQ. This is primarily an academic exercise right now. If an edge appears to be there in a few weeks, I will reassess, but right now I'm not looking at running before I can walk. Appreciate the comments George. And then there was a comment from my NFL Chat-room friend Average Guy, who asks
Hi Cassini, does your stake vary with the calculated value. If the value % is higher is the stake higher ?
Right now I'm just backing (or laying) the value selections (10% edge or more) for a small flat stake, but after a few weeks, I'll look at whether I would be more profitable adopting a Kelly style approach to my staking. Clearly the number of value bets I am finding is too many, but it's a useful 'churn' to offset the Premium Charge, which incidentally hit me again yesterday. It shouldn't be a problem next week though - this week hasn't been a good one so far, and just makes the charge that much more annoying. Had the losses of this week happened a few days earlier, then I wouldn't have had to pay the charge at all, yet just because an arbitrary line is drawn on a Sunday night, and I won before the line, and lost after it, I have to pay. As I wrote earlier in the week, betting isn't like that. Wins and losses are not evenly spaced. Oh well, whining about it doesn't seem to do any good, so I shall shut up.

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