Check out the spreadsheets on LST, specifically within the "U.S. News" category. --LinkRemoved--
On those spreadsheets you can see the % represented by the private salary summaries. For the Class of 2008 information, WashU is actually at 44.5% (~52nd percentile). For the Class of 2007, however, WashU was at 60.2% (~87th percentile).
Now, as far as the response rate goes, it is not as bad as many people will have you believe. Check out this post: --LinkRemoved--. It argues that the picture is really not so bad as far as response rates go. I'm not saying schools have been diligent enough, just that there is a lot data there.
I have long thought this project is amazing, and will say it again (and again, and again.)
I am surprised at how difficult it is to get salary numbers that cover the whole class. My school must diligently track down graduating students... at 72.5% of the class represented by salary info, only Columbia and Duke have us beat. Now, relative to other schools, this is an achievement to be proud of, but 72.5% in a vacuum leaves some room for improvement. It is enough to lead me to conclude that people at or just below median here are not screwed.