All right, here’s the deal with Zillow.com:
I decide I’m going to buy you a pair of designer jeans, nothing but the best for you. I know that fit is important, so I go to three of your best friends to get their sizes. Not yours, theirs. I strike a happy medium amidst the diversity, reckoning that — what the heck! — you can’t be that different from your friends.
If the jeans I buy for you actually happen to fit, this will be a happy accident. More likely, the jeans will be a close but not perfect fit.
You understand why, of course. Epistemological error was built into my sizing algorithm. I chose a method that might have been convenient, but which cannot possibly produce objectively accurate results with any degree of confidence. Arguably, the more of your friends I measure, the smaller my margin of error. But I am still pursuing an inherently erroneous sizing methodology.
For Realtors, a perusal of the tax records, the equivalent of a Zillow Zestimate, is the first step in comping, the step known to be least accurate. The next step is comping the house one-for-one with recent past sales and currently-marketed (competitive) listings. The last step is working all those numbers against the subject property in its current state of upkeep and upgrades.
In the same way, if I don’t take a tape rule to your inseam, the chances of my getting jeans that fit your unique physique are very poor.
However: In email, my friend and client Richard Nikoley set me straight on the value of Zillow.com:
I still think it can be used as a valuable tool for getting an idea of the relative values between neighborhoods in places you’ve never been to. Of course, once you determine where you want to buy, based on a number of factors and Zillow being only one input, then you need to begin the real homework.
Plus which, it’s fun to play with. It would be even more fun in Safari.
The map to the right is a Zillow heat map for Greater Phoenix, reflecting not the ambient temperature (115!) but the (approximate!) price of homes per-square-foot. The swaths of brown are mountains and rivers and Native American reservations peppered with friendly casinos. The blue areas are affordable houses, thousands and thousands of them.
Come get some…
Update: More Zillowography here…
Technorati Tags: arizona, arizona real estate, phoenix, phoenix real estate, real estate, real estate marketing
David G from Zillow.com says:
Haha – Greg, I love this post – very entertaining. I obviously can’t share any secret math but can let you know that you’ve only got one part of the process captured in this story – for example, you forgot to mention that you also took last pair of jeans I bought from my closet and recorded its size – and you did the same with all my friends who bought jeans around the same time … etc. etc. Great post – thanks.
July 21, 2006 — 3:38 pm
Greg Swann says:
No, I understood all that, but the main point stands: You can’t buy clothes to fit without a fitting, and you can’t comp a house you’ve never seen. What you’re doing is remamrkable and fun. It just isn’t comping.
July 22, 2006 — 7:48 am