Monday, 22 April 2019

Pinnacle 3 Football Data 2

For the first time since Groundhog Day, there were two Draws in the English Premier League on the same day this weekend, so the Draws percentage increases slightly to 17.44%, still a clear low for the EPL. 

Four Away wins increases the percentage of Away wins to 33.72%, a clear high for the top tier in England all-time. 

It's not a coincidence that the average goals per game this season is currently 2.826 (more goals means fewer Draws), which is an EPL era high, while the average number of Away goals per game (1.244) is also at an EPL era high.

There's been some discussion on Twitter about the increase in Pinnacle's over-round this season, noticeably in games where there is a short priced favourite.
One suggestion was that it might be due to Football Data only giving prices to two decimal places, even when odds-on. 

I do agree that Football Data should use three decimal places to keep in sync with Pinnacle, but I don't agree this explains the observations this season because Football Data has always used two decimal places (occasionally three) and the big increase has only been seen this season. 

As mentioned, Pinnacle themselves go to three decimal places quite often, as can be seen from the current EPL prices:
The Chelsea v Burnley game tonight currently has an over-round of 102.984%. 

If Football Data round this to 1.26, the over-round drops slightly to 102.921%, but if, heaven forbid, the price is being truncated to 1.25, that makes a big difference with the over-round soaring to 103.556%.

Even with rounding in play, which I presume is the case, that extra digit can make a big difference, with a price of 1.255 being recorded as 1.26, the same as 1.264. Using the Chelsea game above as an imperfect example, but for the sake of argument, a 1.255 price would give an over-round of 103.237% while a 1.264 price gives a value of 102.67%. (In practice, the Draw and Away prices would move, but this example illustrates the difference rounding can make).

Looking at matches where the home team is priced at 1.3 or shorter, the average over-round between 2012-13 and 2017-18 ranged from a low of 102.04% in 2016-17 to 102.21% in 2017-18, before this season's jump to a current 103.08%. 

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