When using implied probability with betting odds, I get a weird result, that I cant seem to understand.
I should say I am looking at betfair exchange, so the odds are not set by a bookmaker, but by other betters.
When I take the odds, and calculate the implied probabilities, I do not get a sum of 100, which I think is odd.
The example goes:
$1 / 2.68 \times 100=37.31$
$1 / 2.78 \times 100=35.97$
sum = 73.28
I know bookmakers take margin, so the sum usually is above 100 (like 105 for example), but I have never seen it below.
And even better (for me), with both odds > 2, I can bet both an get a sure profit (arbitrage). So I don't understand this..