over the past 5 years I have consistently seen lines on the dogs go down and down and down........
I think part of the reason is that the casual player is much more apt to playdogs now which has resulted in the fact that the linesmaker has adjusted the number.
Also early in the season so the #1s are still often lined up against other #1s. Once you get more days off, missed starts, injuries, etc., you will see the #1s going against #5s and #4s and will have bigger numbers.