W/R/T Housingtracker.net - their data is pretty suspect. No, make that useless. I quit looking at it months ago.
They seem to do no reasonableness checking and report things like the change JimN refers to for months on end when to any informed observer it is clear they have a data feed problem. Today, they are reporting roughly 14,00 SFH+Condo listings in Seattle/Tacoma/Bellevue. Based on their description, that's for all of King and Pierce Counties. Tim's count for those counties - which tracks to NWMLS pretty closely, is over 24,000. Do you trust them? I don't
Their business model is to collect eyeballs for ads - and I can't say that I sense a lot of care about what they are reporting.
if you want good data on what is happening to listing prices, go over to Altos Research. They actually make a living selling their analysis of data back to bankers, realtors, and buyers. It has to be accurate. You can also get data on every community in Washington of any size.
http://www.altosresearch.com/research/WA/Seattle