Working With My Zestimator
By: Stan Humphries, VP, Data & Analytics | February 13, 2006
Since much of the feedback so far has been in the area of data and Zestimate accuracy, we thought it couldn’t hurt to give a little overview of the My Zestimator tool. Lloyd already discussed it a bit in his earlier post, but here’s more detail for those of you who might be encountering inaccurate data on a house, want to refine the Zestimate with some additions or renovations to a home, or need some tips on using My Zestimator.
When we set out to create Zestimates, we quickly realized that we could only go so far in assigning a value to every home in the U.S. from the cramped confines of our current offices in Seattle. It was obvious that people would have a vast amount of knowledge essential to truly understanding home values in their own neighborhoods that we simply don’t know about here. It was from this realization that the idea for My Zestimator was born. My Zestimator is an interactive tool that you access by clicking on the “Refine value of home with My Zestimator” link on the details page for a given home. (The link is just below the Zestimate figure. After you go through the four steps of My Zestimator, you will get a summary page similar to the attached screenshot). By using this tool, a user can come up a more accurate Zestimate by updating four specific areas important to the valuation process:
• First, if you see outdated or just plain wrong data on a home, you can correct the basic facts. For example, say the Home Facts indicate that you’ve got two bedrooms, but you really have three. In the first step of My Zestimator, update the bedroom count from 2 to 3. Remember to change the square footage accordingly.
• In Step 2, you can add in details about home improvements that have been made to the house. Fill in details about any updates you may have made, such as a remodel to a kitchen or a deck addition.
• In Step 3, we give you the opportunity to add other special attributes about the home which you think either add to, or subtract from the value of the home. For example, here you might add some value for a view of the mountains or subtract value for being next to a landfill (stay tuned for more thoughts in the future about whether landfills are really that bad for resale prices on surrounding homes!).
• Lastly, in Step 4, we come to what I believe is probably the most powerful aspect of My Zestimator – choosing comparable transactions. Here, you can tell us about other nearby recently-sold homes that you believe are great comps to the current one. From amongst a list of up to 50 comparable homes around a given house, pick up to 10 homes that you feel are really very similar in key ways to the current house.
Right now, My Zestimator works best for users who complete all four steps of the process. We’ve gotten a lot of feedback from folks who’ve completed Step 1 (Edit Home Facts), received curious changes in the home value at this stage, and bailed out without completing the other three stages. The reward will be greater if you hang in to the end since the physical data on the home is best evaluated in the context of homes that you’ve indicated are good comparables for a property.
In some cases, you might still find that My Zestimator is quite sensitive to small changes in inputs. This sensitivity has to do with the particular characteristics of data around your home on that particular day (since we’re adding new data all the time). We’re working very hard to make this tool even more robust and think we’ll have some good results to share with our users in the coming months. We’ve not seen many other tools quite like this one that works on the fly, so we think it’s a cool and very promising tool. The specific feedback that we are currently getting is very helpful in our efforts at improving My Zestimator and I’d like to encourage folks to continue telling us what’s working and what’s not. And we can’t wait to show you what we’re cooking up next on this front!
- Stumble it!
- Categories: FAQ, Zestimate, Zillow
Comments
40 Comments so far
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Chris L on February 13, 2006 4:06 pm
Zillow is an awesome spoof site. You’ve got everyone convinced and its not even April 1st! Clever.
Clever marketing and a fun site, but ultimately a very well-composed spoof. 5 stars for effort and originality.
I was amused to find that my house showed up as $2.67M property - that’s over 10 times what it’s actually worth. And its interesting how in my street, the most valuable property is also (coincidentally) the one I search for. So if I look for my house, it’s the most valuable. If I then re-do the search with my neighbour’s house, theirs is now the most valuable. Looks like the same is true for any address in Utah - all of zip code 841xx according to zillow is almost a billionaire neighbourhood
3 cents on February 13, 2006 6:27 pm
the data you cull to crunch a zestimate is not accurate or complete and may be outdated. Some public info is not even available until months after a sale. The modifications for improvements are subject to cost variables which are not constant. Price paid for an improvment is not an accurate indication of it’s contribution to overall value. rising markets and falling markets render the Z unusable. try as you may to sell the kelley blue book analogy, which you must to dupe the consumer into believing the estimates are worthy of use, houses are not cars by any stretch of your marketing imagination. And brokers are not used car salesman selling commodities with little or no uniqueness. If anyone embraces the Z, they will become its prisoner. If you were anyone other than Mr. Barton, you would be laughed out of town. People, the emperor has no clothes!
Amy Bohutinsky on February 13, 2006 6:54 pm
Hi, Amy from Zillow here. In response to Chris L’s comment about his neighborhood in Utah: we have a known issue in certain parts of Utah that is affecting the accuracy of Zestimates. We are switching to showing just tax assessments in those areas this evening until we fix this issue. We anticipate the Zestimate fix will take a few weeks. Chris, please check back and let us know what you think once we’ve reinstated Zestimates for your area. Meanwhile thanks for your feedback and helping us make Zillow.com better.
3 cents on February 14, 2006 12:17 am
Brokers will praise the zestimate when the numbers are to their liking and denounce it when they aren’t. The only problem for the buyer or seller is knowing THE TRUE VALUE (what the market will bear).
I challenge any seller to sell me his house based on a Zestimate (it’s just like Kelley blue book value, right?) —one condition— no one gets to peek until after the contract is signed? any takers? I didn’t think so.
Amy, answer me this—if PEOPLE are able to tell if the Zestimate is wrong, why do you need a Zestimate? People: rely on your far more sophisticated machine—your brain.
David Saks on February 14, 2006 5:22 am
Hooray for Zillow,
You are absolutely a most welcome addition to the lives of the real estate consumers and professionls throughout the country. With the recent problems plaguing the real estate industry along with the cries of “anti-trust” and restriction of free trade by the Department of Justice and others, being hurled at industry icons the likes of the National Association of Realtors and local real estate organizations, making this extraordinary volume of information available places unprecedented power in the hands of those who otherwise would not have been able to make informed decisions regarding their investments, either current or pending. In addition, with the rise of predatory lending, mortgage fraud and the risk of foreclosure facing so many low income households throughout our country, Zillow will impact the lives of millions by making the tools available to assist many families facing catastrophic ruin by helping them make responsible decisions regarding their efforts to purchase, refinance or recover from the threat of a marauding, predacious and unscrupulous threat which victimizes the unfortunate for personal gain. I applaud you, Zillow. “Three Cheers for Zillow”!
Best wishes always,
David Saks
The Real Estate Mart of Tennessee
Memphis
Chris L on February 14, 2006 8:03 am
Amy - I checked again this morning and it’s still showing house prices in the millions. Sorry for the comments above - I genuinely thought this was a spoof site.
Jessie B on February 14, 2006 3:20 pm
Hello Guys, great work and great UI. I think that what is needed is a bigger disclosure to consumers stating that this is an estimate and maybe add in a typical margin of error and source of data (to explain GIGO of some results) for the area you are providing a “Zestimate”. I did some research regarding the accuracy of the Zillow estimate which I charted for Southern California (good data) and it seemed fairly accurate on average but with occassional big swings… in case your interested: http://www.forsalebyownercenter.com/blog/
Amy Bohutinsky on February 14, 2006 6:58 pm
Chris - I spoke too soon. Check back in a couple of days and you should see a change.
Mike S on February 16, 2006 5:11 pm
I find it odd that the zestimator ‘punishes’ value for more bedrooms and ‘awards’ value for fewer. A particular house I was reviewing was wrongly listed as 3-bedrooms, I corrected it to 4-bedrooms and ‘lost’ $40,000 (even with added square footage). Then I dropped the bedroom count to 1-bedroom and gained $200,000 plus. I don’t get it.
3cents on February 18, 2006 12:50 am
I find it interesting that the value of Z, i.e, its accuracy, is determined by PEOPLE looking at it and saying “it’s off by this or that”. What does that tell you? It should tell you that whether an estimate is provided by the zestimator, the Terminator, Deep Blue or any other non-human number cruncher, there is none better than the “grey matter cruncher”, your brain and a little common sense. Let’s all get some and leave those not willing to exercise their brain to push a button for a zestimate and then ask a pro “Is this right?”
3cents on February 18, 2006 12:53 am
ps. Watch for the “positive” post to come now to distract you from my “negative” comment
Michael McClure on February 18, 2006 1:03 pm
I own a real estate company (you can see it at ProfessionalOne.com). I have been selling real estate for 15 years. I am also a CPA, so numbers “are my thing.” I am HORRIFIED at how inaccurate your information is. My home, for instance, is worth approximately $450,000 to $500,000. Your site shows it as being worth $157,000! I put an addition on my home several years ago that cost more than your estimate of the entire value of the home! If this doesn’t get your attention, then you are flat out negligent. Most of my agents have checked out the values of their homes on your site, and 100% of them have indicated that your estimates are not ever close! This spans seven different communities located in three different counties. One has a home worth approximately $270,000 - your site estimates the value at $117,000! This error percentage is OUTRAGEOUS!!! I’ve also had several unpleasant encounters with clients of mine that are ASSUMING your site is accurate. I would suggest you do some MAJOR site enhacements ASAP, because the uproar that is building within my industry is like nothing I’ve ever seen or felt before.
Judy Wilson on February 19, 2006 8:29 am
I find the information for my area in Texas quite accurate. Current viewiers need to remember this is a “Beta” site. It may still need tweeking, but overall a valuable site for a home buyer or seller.
Jim Meisinger on February 20, 2006 9:53 am
Dear Zillow,
Where does your data come from?
Jim
Stan Humphries on February 20, 2006 12:57 pm
Hello, this is Stan from Zillow responding to Mike S’s question. Mike, please try continuing to Step 4 of the tool and picking some comps for the home. In Step 1, data from a broader geography around your home is used and, in some cases, these interim results may not capture the dynamics closer to your home. In this event, the result is usually corrected once we have specific homes that you believe are good comps. Very soon we will have an improved methodology behind this tool that better considers the context in all steps, but we hope that, for now, completing Step 4 corrects the issue for you.
Mike S on February 20, 2006 11:56 pm
Thanks, Stan, for the response to my query regarding valuation fluctuations as per bedroom count (they seem counterintuitive, and in exact reverse relationship to what one might expect…e.g. fewer bedrooms equal higher valuations). I’ll try adding in more comps to the specific properties in question and see what happens. I’ll let you know. Mike
Mike S on February 21, 2006 12:18 am
As I included comps with a higher $/sq ft ratio, it raised the total price as an ‘add-on’ value, but it still included a $44,000 loss in value for identifying the property as a 4-bedroom, rather than a 3-bedroom, which is the mystifying part to me.
I do understand that proper ‘comping’ will adjust for like to like properties, as well as the step that allows ‘upgrades’ to be quantified, but the programming theory behind ‘fewer bedrooms produces higher values’ with no other variables changed is ponderous (similarly more bedrooms equals lower valuations, even if appropriate square footage adjustments are included to complement the extra bedrooms. That part is still a mystery.
As an active Realtor, we are well aware that a 4-bedroom house commands a higher price (and therefore value) than a 3-bedroom house in these neighborhoods, even if the square footage were unchanged, but especially so when the square footage is raised to compensate for an additional (in this case a 4th) bedroom.
Just curious as to why the formulation is programmed as such, since it otherwise, just appears wrong. More than curiosity, really, in that we are hoping to be able to use your services as a tool to help identify (retail/for sale) pricing anomolies in our marketplace. Mike
Jason on February 21, 2006 7:56 am
Stan from Zillow, I have a question for you. I live in a suburb of Detroit and my Zestimate is off. I went through the My Zestimator tool to try and correct the home data and choose relevant comps. What I discovered is that the comps that I can select from are all 10.5 miles west of my house. The initial Zestimate tool shows comps that are reasonable in selling price and distance from my home (up to a mile or so), but those comps disappear when I use My Zestimator and I am left to select from houses that are 5 zip codes away! Please investigate this and at least tell me that you see the problem and will fix it when you can.
Barry N on February 21, 2006 1:57 pm
As an Appraiser and Broker, I have used your site to check the value of four properties that were recently accurately appraised. (1) was $54,000 under its Current Market. (2) under its Current Market Value by $84,000 (3) surprise, over its current Market Value by $36,000
(4) under its current market value by 125,000 (5) within $10,000 of its Current Market Value. Also, a lot of the County Records data is outdated and inaccurate - as you do point out at the site - is there an alterate agenda at Zillow? Are you doing this, hoping to talk thousands of home owners into giving you more accurate data on their homes, so you can later provide Computer Model valuations for the banks, who want to break into brokering as well as lending to control property valuation and manipulate the industry and the Market? (National Association Of Realtors)
Dave S on February 21, 2006 7:25 pm
Since I retired from the appraisal industry after 33 years, I thought I would do some minor research after purchasing my new home build to see what the market trends were now. I was appalled to find my home valued by Zestimate at $165,000 which actually was the land price. To make matters worse, the comparables were of 20-30 year old homes in deteriorating neighborhoods in the $165,000 range. In Denver, that is nothing for a single-family dwelling. So I suggest you refine your comp search to determine, at a minimum, which sale prices are vacant land only. And don’t use the sale price as the basis for comparability. That can only happen when you are comparing apples with apples so-to-speak. You need some refinements and I suggest you seek appraisal professionals to assist you. I must say you do have some good looking screens! Keep working you might get there yet.
3cents on February 21, 2006 10:26 pm
Wow. After reading the latest comments, my faith in human beings is restored. If house valuation by machine has to be checked by human beings (and everyone who uses it DOES CHECK TO SEE HOW OFF IT IS), what real value does it serve? It merely creates another obstacle between buyer and seller. The naked emperor has at last been seen.
Stan Humphries on February 22, 2006 11:44 am
Jason: I received the address for which you’re having issues and will follow-up with you directly. Thanks.
gabriel on February 22, 2006 3:24 pm
My home is way over-valued! I don’t get the purpose of the site. Can I sell my home on your site or send me to someone who can help me sell my home?
TONY on February 24, 2006 7:13 am
I CANNOT GAIN ACCESS TO MY ZESTIMATOR. IS THERE ANYTHING I NEED TO DO PRIOR TO GAINING ACCESS TO MY ZESTIMATOR?
Glyn on February 26, 2006 9:56 am
You have listed my house as 1100sf,2 beds 11/2 baths.In actual fact it is 2400sf,4 beds and 2 full baths.If you cannot get the basics right how can any one trust the so called fact you are giving out.
Steve Cabito on February 26, 2006 2:42 pm
Hi - I like your concept so much that I’d like to create a Firefox search plugin for it. The plugin architecture only allows one argument to be passed. Is there a Zillow URL which will accept a query of the form
http://www.zillow.com/
search/
Search.z
?addrstrthood=123+main+st
&citystatezip=99999
&mode=search
(above all on one line)
which will enable me to enter an address with a zipcode as the last term?
David Ruma on March 2, 2006 9:09 am
Zillow is great! The only problem I found is that in my county the house value was based on the “taxed” value which is 35% of the actual market value. Zillow is showing the reduced valuation, which is misleading users looking at homes in my area. It might be hard to sell your house if a potential buyer sees a valuation that is 65% less than the county appraisal! Work out the bugs and this system is great.
Randy on March 2, 2006 2:18 pm
I applaud you all for biting off such a huge and needed chunk. Keep your open minds…the criticism will make you better and better.
Thank you so much.
Robert A McCormack on March 3, 2006 2:31 pm
What are you using as source data for computing price appreciation for a particular town township or zip code and how do you go about getting this information from the web site. THANKS I think an answer to this question wold be helpful to many users.
meg on March 4, 2006 11:10 am
Two comments on the zestimate:
First, for my home, the zestimate value was wildly overstated. (zip code 060XX) I went through all the steps to update the information in My Zestimator, including selecting 10 comps. All comps had been sold between 5/05 and 10/05, and averaged $432k. The “refined value” for my house was $732k. If only. Real estate values in my area (as in many other areas) have been trending slightly down since 10/05. Even if that were not true, I’d like to see the real estate market where values go up 70% in four or five months. Seems like a programming error.
Second, a major piece of missing data is home style. In my market, a 2,000 sq. ft. raised ranch or split level is worth quite a bit less than a 2,000 sq. ft. colonial. This is a pretty glaring omission, IMO.
Otherwise, your site is addictive.
Elaine Carter on March 13, 2006 8:42 pm
If I am unable to locate a specific home using a true address could it also mean that the person lives in a trailor home? Thanks.
jillee on March 24, 2006 2:12 pm
Get this! Zillow is listing my home address as belonging to a totally different house all together! AND My street is listed on the other side of town -where there is no street with my street’s name! The house that my address shows is 1400 square feet smaller than mine,in a less prestigious area, and comes in over $200,000 less than my home’s value! When I scroll north on the satalite view, I can find my house, however, the satalite says that there are no homes in the area!!!???? HUH?
I would rather Zillow take my address totally out of their database, NOW!
I live in a vacation home area. People who are buying homes in this area are not locals.
That means, if someone were to look up my home’s address, not only would it be the wrong home, but the home that comes up is overall not in the same BALLPARK as mine! Our home is in an area people refer to as ‘Knobb Hill’ as the homes overlook hundreds of miles in all directions. The home that Zillow shows as my address is accross the lake from us in a valley! We wanted to put our home up for sale in April, but this zillow estimate will be a devistating blow for us! Buyers are looking to Zillow as if Zillow were God’s truth!
For those who type in their address and find that Zillow has priced your home OVER market value-My advise is - SELL NOW!
Tim O on March 28, 2006 4:31 pm
Seems like this site is going through some growing pains! Looks like a great idea. Our home in Mpls, MN is right on the money. Good luck keping up with the changes Zillow!
JOHN STANWIX on April 13, 2006 4:00 pm
HOW CAN I MAKE CHANGES ON THE INFORMATION ABOUT MY HOUSE. SOME OF THE INFORMATION YOU HAVE IS INCORRECT. I BELIEVE YOU RECEIVED INFORMATION FROM PROPERTY APPRAISERS OFFICE AND I CAN ASSURE YOU THAT ALL APPRAISAL — ASSESSORS INFORMATION IS NOT CORRECT. IWAS A REAL ESTATE APPRAISER AND A ASSESSOR AND I KNOW THE INFORMATION IN MANY CASES IS NOT ACCURATE.
Debbie Stinson on April 13, 2006 6:22 pm
Zillow is a fun and useful site. My house, too, has some inaccuracies, but I can appreciate that Zillow is still in its infancy and not intended to be the sole resource for buying or selling a house. I’m particularly impressed by the new “Birds Eye View” feature and am looking forward to expanded coverage. I am currently shopping for a new house in a different part of the state, and it really helps to be able to see the neighborhood and immediate surrounding areas, which you don’t get when viewing pictures of homes for sale on the big real estate sites.
Larry Merrill on April 14, 2006 4:53 pm
Stan from Zillow…when will NH information be available? Interested on the seacoast.
Sharon Fitzmorris on April 15, 2006 7:49 am
I liked your site. Although the last three days I have not been able to look up property values it keeps telling me that the site can not perform the zestimate and I’ve used several differnt homes that I had checked previously and it could not perform the function. Thank you for your interest. Sincerely, Sharon Fitzmorris
Ryan Beesley on April 23, 2006 3:12 am
Hello, this is Ryan from Zillow.com.
Steve Cabito, I don’t know if you’ve seen it or not, but when we released the Bird’s eye view feature, we also added our Zillow Labs ( http://www.zillow.com/labs/Labs.z ). In this, we have created a Firefox search add-on, and a control that you can put on your own webpage.
I don’t know if this is what you trying to create in Firefox, but I’m afraid that our current search design requires an address parameter that is seperate from the city/state/zip parameter. If there is something else you are trying to do, let me know and I will do what I can to assist you.
steve graham on April 23, 2006 11:24 am
Where do you get the square footage? My house at 8453 se woodcrest pl hobe sound, fl 33455 is listed at 3100/ actually is 4600 with 3700 under air!
Mary Ellen Speer on April 27, 2006 10:43 am
OUR HOME IS NOT FOR SALE…
I just heard about Zillow.com from a TV program and started to play with information about properties including ourselves.
We purchased our home 1958 and would be carried out of it kicking and screeming. I was totally surprised at the Zillow zestimate. Of course nobody would know how we have updated and taken care of our personal property. I would be pleased to update all the improvements we have made to our property over the years.
Please let me know how to do this.
Thank you
Mary Ellen Speer
5380 Ridgeway Drive, Box 63
Old Zionsville, PA 18068