Odds comparison sites

I don't think so

Having worked for a bookmaker whose prices appear on an odds comparison website, I can tell you that the prices that you see are not a reflection of the probability of the outcome in the bookmakers opinion

If you fancy that the probability of something happening is 6/1 and the best price out there is 3/1 you would mark up 100/30 or 7/2 to attract custom

[x], exactly. The variation in tissue prices between bookmakers, let alone between serious punters, is huge. The differences in price offered are minuscule, to prevent arbing.

Were there a tote monopoly with a tiny overround, racing might in all probability make more than it does now, as there would be no alternative for winning price-takers / price-makers to stand their opinion.

Notwithstanding the skills of some of their employees (increasingly sidelined), bookmakers' activity would be seen correctly as parasitical, and perhaps a handful of winning punters would be seen as the price of a greater volume of custom.

(should have added that it's football only though)

cosmic:

I use txodds, they provide average odds but also more usefully, they use those odds combined with the overrounds of each bookie to estimate probabilities (which I assume is what you wanted to do with them?).

I would be interested in a study too. Overnight odds are a lot less accurate than sp odds.