Question regarding price change influence

[tiberigc]

I heard the saying that "when you back a horse, you essentially lay the other(s)" or "when you lay a horse you basically back the other".
Is that theoretically or practically speaking? By this I am asking, are the amounts of money you are 'backing' in the ladder, splitting between the rest of the horses in the lay field?

Lets assume we have a 2 horse race and on one horse there is no activity, no one matching amounts, lay and back sums are only idling at a certain price.
Will backing/laying on the first horse move the price of the second horse although the amounts are not getting matched for the second horse? If yes, how is this possible?
If I am to lay the second horse at 2.0 odds and no one is matching, how is a lay on the first horse going to push my odds?

Sorry if the question doesn't make too much sense, English not my first language and I am thinking out loud in my native tongue

[spreadbetting]

Betfair employ what's called 'cross matching' on the markets so in a two runner race laying a horse at 2 is the same as backing the other at 2 and betfair will

I heard the saying that "when you back a horse, you essentially lay the other(s)" or "when you lay a horse you basically back the other".
Is that theoretically or practically speaking? By this I am asking, are the amounts of money you are 'backing' in the ladder, splitting between the rest of the horses in the lay field?

It's practical as betfair use what's called cross matching. In your 2 runner example a lay at 2 would also appear as a back at 2 on the other runner. With more than two runners Betfair use the aggregate book percentages of all the other runners to recreate the opposing odds.

https://www.youtube.com/watch?v=Bys1lu-18wo

[tiberigc]

thank you sir, short and concise