Shops with small amount of volume will eventutally ALL go to a -20 line for baseball.
If you will notice lots of times you can beat the price, very slighty at the -20 joints if you want to be chalk player.
I noticed last year that at Cris which is a -20 shop was leaning to almost ALL dogs, so in turn that made the favorite at Cris less than some of the other shops.
Just remember to take a look at this if you are a chalk player. I am not so it never helps me anyway.