Dutching Across Exchanges

[robjag]

Good morning all,

Please could someone help me understand how the odds/prices are calculated on the various exchanges?

I've been developing a spreadsheet that dutches UK horse races, which more or less gives a positive return. I had the 'genius' idea of dutching across betting exchanges because, so my thinking went, the prices of each exchange are bound to fluctuate wildly compared to each other, particularly in the few minutes before the start.

What seems to happen though is that all the prices on whatever exchange I look at track each other pretty well exactly, as though the odds were calculated centrally and then distributed to each exchange. I had thought that the bets placed locally on that particular exchange set the prices for that exchange specifically, but apparently not.

This phenomenon definitely applies to horse racing, and also to the other markets I looked at such as tennis.

My understanding of calculating the odds is obviously flawed ... please could someone set me straight?

Many thanks,
Rob

[Dallas]

All exchanges are independent but there is an army of bots already doing exactly what you've just thought of so you'll find very few arbs and will have too be very quick if your going to profit from one

[robjag]

All exchanges are independent but there is an army of bots already doing exactly what you've just thought of so you'll find very few arbs and will have too be very quick if your going to profit from one

Oh cool - understood! .. so there's hope yet! Many thanks