Mean or Median - A Few Thoughts on Average

Posted on May 10, 2011 by Corey Hart



Around the 8th of each month, I get an email from Betsy (our resident data geek) with a first look at the previous month's data. I then start bugging Porter (data visualization geek) to push them into our staging environment so that I can take a look at the new Interactive Charts.  A little perk from working at RBI - getting a sneak peak at local RE stats while the finishing touches of QA are applied (and before we update our site on the 10th!  Being a Loudoun resident, I usually jump right to the LoCo page to see how the market is trending and how my ZIP code is looking. Though unlikely since I've been in NoVa for decades, I occasionally toy with the idea of selling my place and moving to Maryland (2-hour commutes like yesterday makes it all the more tempting!), so obviously I like to keep tabs on recent trends.


Diving in this month, something jumped out at me when looking at the townhouse segment - the average Days on Market before sale was somewhat higher than I'd expected, given what I've seen from neighborhood signs changing from "For Sale" to "Under Contract" as I drive around (can't get much more anecdotal than that, but hey, I'm not a REALTOR®).  The chart below shows the Average Days on Market for the 225 detached sales (in purple) and 134 attached sales (in red).


I realize most agents (and home sellers) in counties outside of the MRIS region would love to see such relatively low figures, but the 45 day average for townhouses and 92 day average for detached homes still was higher than I'd expected. I flipped the Interactive Chart over to Median DOM and found a picture that better fit my preconception:



Hmmm, so 67 of the 134 attached units that sold in Loudoun took less than 3 weeks? And half of the 225 detached homes took less than 2 months? Both numbers are remarkable to me...and no doubt will come to mind the next time I'm sitting idly on the Dulles Toll Road pondering my options. The median gives the outliers - like the home that sits on the market for 8 months before selling or the foreclosure that went to market at 70% of it's true value and sold in a day - much less influence on the picture. The bottom line is that agents should understand and explain the two types of averages, it often makes for a more compelling answer to the question "How's the market?".

interactive charts, rbiEXPERT, rbiPRO
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