The scale on this chart goes from +40 to -40
People like Kucinich, Lee, Tubbs-Jones, Waters, Watson, Woolsey, Corrine Brown, Clay, Clyburn, Conyers, Evans, Filner,Grijalva, Hastings (FL), Jackson (IL), Jackson-Lee (Tx), E.B. Johnson, Kilpartrick, Lewis (GA), Markey, Owens, Pallone, Payne, Schawkowsky,
and Thompson (MS)all have +40 as they took the time to vote and all their votes have been great.
Those who have missed one vote but otherwise voted correctly are at +22.5
Those at + 20 blew one vote but voted correctly on the others.
There are some Democrats who are at -40 because they've voted with the Republicans every time.
Pelosi is at +2.5
0 means half their votes are with the Republicans.
The House chart only rates Democrats.
http://patrickhenrythinktank.org/house-scores.html