I'll go ahead and jump in before, Dallas is helpful - as always - and posts a link to Betfair's historical data

We all - or I should say those who have been doing this for a bit - know intuitively (for lack of a better word) what kind of liquidity to expect in different markets at different times leading up to the start time. That said Derek's comments in another thread, on the common sense of not entering a market with more than realistically can be traded out, got me thinking that this kind of data sorted correctly would be of great benefit, as a reference point, to everyone, hardened veterans and newbies alike.