Originally Posted by
Thunderground
I have that as part of my program, so will chip in.
The total percentage, of the combined odds, is different per track. For Belmont it may run from 120 to 128 percent, in prerace betting, and then after the race the final percentages settle around 120, or a little lower. That's because 5/2 (250) can be as high as 290, but will not show up on the tote board as 3/1 until it reaches 300. For a track like Turf Paradise the total prerace odds are often around 135.
Also, the odds are often manipulated around a big favorite. That is, a big favorite may show as 3/5 (60) on the tote board with the total percentage going up to 128 or 130. That means they're making room for that favorite to go to 4/5 (80). In other words, all the other odds are adjusted first before the big favorite moves. Once the favorite moves to 4/5, the total percentage suddenly drops to the 122 or 124 range. So the total percentage is not a constant at all in prerace betting.
If the tracks were to change to sports betting type of odds, +100, +270, +425, the total percentage could be kept constant, but with odds like 3/2 and 7/5 and 9/2 that's not going to happen.