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Entries Tagged as 'Real estate mapping'

Bay Area Housing Price Trends … In A Map

July 30th, 2007 · 2 Comments

After a wonderfully fun — and occasionally frustrating — evening of hacking around, I’m please to present this mashup of Bay Area housing price trends. The graphs are from our friends at Altos Research, and the Google Maps were created using Zeemaps from Zeesource.

For a larger map, click here.

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Tags: Altos Research · Consumer · Google · Industry · Mapping software · Real estate 2.0 · Real estate data · Real estate mapping · Zeemaps · Zeesource

Zestimating Zaccuracy of Zdata

September 22nd, 2006 · No Comments

While Gregg Swann was busy stirring the pot again (another post sure to bring wrath and retribution raining down on him) and the good folks at Sellsius were busy Carpal Tunnel-ing themselves (don’t these guys sleep?) and Patrick Kitano was explaining my friend Chris Iverson’s real estate “money back guarantee” (heck, if I weren’t an agent myself and I didn’t work for a competing broker, I might just take him up on it!), I was busy trying to answer a question I posed two days ago: how accurate is the data on which Zillow bases their controversial Zestimate?First, a big, big, big, HUGE up-front disclaimer, in keeping with many recent discussions: An automated valuation mechanism (AVM) a la Zillow is not and never will be a substitute for an appraisal done by a professional. It is an estimate, and an estimate only. Improving the accuracy of the data on which the Zestimate is based will not change that fact. ‘Nuff said.Based on my initial highly unscientific look at 10 randomly chosen properties in Menlo Park and comparing the data about those homes as presented in our local MLS vs. county records vs. Zillow, the county gets an accuracy score of 87%, and Zillow gets 84%.I intend to add a number of additional cities to the mix and see what patterns emerge. In the meantime, here are the results… (if you’re a numbers jock and interested in my scoring methodology, scroll down below the chart.)

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Tags: For buyers · For sellers · Fun with Zillow · Real estate · Real estate 2.0 · Real estate data · Real estate mapping · Zillow

Fun with Zillow — #5 — Don’t invite David Blaine or David Copperfield to your home

September 20th, 2006 · No Comments

Zillow-bashing is a favorite pastime in the real estate blogosphere, second only to its cousin Redfin-bashing.

The Zillow bashers have (at least) a triumvirate of beefs with Zillow:
1) Its raw data is suspect
2) Its home-valuation algorithm, even if it were based on good data, could not possibly lead to an accurate Zestimate because it doesn’t, and can’t, consider non-quantifiables like views, amenities, smell, etc.
3) To protect consumers from over-reliance on a Zestimate, Zillow’s home page should have a big, bold disclaimer about 1) and 2).
In an effort to address 1) above, Zillow today announced that home owners would be able to “wikifi” their home’s data if necessary.
So is Zillow’s raw data (mostly from county records, I believe) really that bad? The results are in from a quick, highly unscientific study comparing Zillow’s data on 10 random properties in Menlo Park, CA, with local MLS records.
The county got 6 properties completely right. Of the remaining 4:
  • One was off by half a bathroom. Not so bad, unless you’re visiting there and drank too much beer.
  • One was missing a full bathroom, a bedroom, and 800 square feet. Better not invite too many guests!
  • The third had the correct square footage, but two bedrooms and a half bath had disappeared. Maybe that’s David Copperfield’s home?
  • The final one was missing 6 square feet of lot size (not a real problem since the lot in question was 21000 square feet), but the home itself was missing! Maybe David Copperfield and David Blaine lived there?

Zillow scores 90% for its data feed. Zillow had the right information for the 6 properties that the county had correct, and it had the same incorrect information on 3 properties that the county had. The final property (the David & David home) simply wasn’t there!A challenge to my fellow bloggers out there: If you have access to your local MLS and want to run a similar experiment, email me at and I’ll send you a link to an iRows spreadsheet I’ve set up.

Here are my results:

Tags: , , Heat maps, , Microsoft Mappoint, , , , , , Zillow heat maps

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Tags: For buyers · For sellers · Heat maps · Mapping software · Microsoft Mappoint · Real estate · Real estate data · Real estate mapping · Technology · Zillow · Zillow heat maps

Heat maps #1

September 19th, 2006 · No Comments

I’ll have to cross my fingers that Zillow hasn’t taken a page from Redfin’s book and trademarked the phrase “Heat maps.” I’ll take my chances…

I’ve been using Microsoft MapPoint for nearly three years now to present real estate data to my clients in an intuitive format.
Exhibit 1: Schools and neighborhood income

The little peach-and-yellow pie circles represent schools, with the amount of peach shading indicating that school’s academic performance (as measured by the API index) compared to all other California schools.

The green shading represents neighborhood incomes; the darker the green, the higher the median income, as measured by the 2002 census.

1 — (two spots) Very, very light shading; low income neighborhoods populated mostly by Stanford students. This is where many Silicon Valley enterpreneurs get their start-ups going.

2 — Moderate green shading; moderate income neighborhoods. This is where Silicon Valley enterpreneurs move to after they graduate and get their first round of angel financing.
3 — Dark green shading; very high income neighborhoods. After their start-up goes public, this is where the enterpreneurs move, to towns like Atherton.
4 — Dark blue lines indicate school district boundaries.
5 — A very good school, as indicated by the near full shading.
6 — An average school, as indicated by the ~50% shading

Tags: Heat maps, , Microsoft Mappoint, , , , , , Zillow heat maps

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Tags: Heat maps · Mapping software · Microsoft Mappoint · Real estate · Real estate data · Real estate mapping · Technology · Zillow · Zillow heat maps