Astute observation. The MLS search mechanism is somewhat crude. For instance, you can do a search on actives, pendings, solds, cancelled, withdrawns etc…You can specify timeframes as well. For instance, show me how many sales or cancellations occurred for listings that came off the market between oct 1 – oct 30, 2006. If you listed your home, and then your listing was expired or cancelled, then you relisted, your active listing is considered new. This is not the case for withdrawn because under withdrawn status you are still under contract. The clock stops (with regards to the days on the market) and when the listing is moved from withdrawn back to active the clock starts again.
One very useful item in the MLS is the listing history. You can look at the listing history for INDIVIDUAL listings and it gives you the chronology of the listing, like when the prices have changed. Again though, the history is ONLY for that particular active listing. The history will never tell you that that listing ever expired or cancelled.
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Unfortunately when you go to the statistics page you get overall information, not information on individual listings.
Say I did a search on actives for a particular zip code, and found there were 110 actives and then I did a search on expired/cancelled/withdrawns for the same zip code for homes that came off the market within the past 90 days and found there were 50, I would have to manually look at each list and cross compare to see what you are looking for. The MLS may have a way to automatically do it but I do not know of it. Other Realtors may and hopefully they will post it.