Why does The juice on a line change?

[hooks26]

This may be' a stupid question! It say texans+3 -120 ravens -3 +100 why does tge juice move and not The line?

[GFootsXtreme]

Historically the Bookmakers can look at the results of every NFL game that has ever been played and they have statistics telling them, and us, exactly how often they should expect certain results.

They know how much "value" there is in every line move, and moving a line from 3 to 2.5, or 3.5, is the most "valuable" move there is.

So to move a line off of 3, which happens, takes a LARGE, LARGE amount of money, relative to any other number. They move the juice as a "miniature line move" within the 3, so to speak.