Zestimate Accuracy

52 Comments so far

1. Alan on October 27, 2006 7:51 pm

   Zillow.com may possibly be more true to NCRC’s mission than the consumer group itself. The first line of their mission states: “NCRC’s mission is to increase fair & equal access to credit, capital, and banking services/products because discrimination is illegal, unjust, and detrimental to the economic growth and well-being of our society.” Was it Zillow.com that that allowed millions of Americans to refinance their homes at well over the price that the local market could support? Many of which could be categorized as predatory lending towards the sub-prime market. Is Zillow.com a partial appraiser collecting money from a mortgage or real estate broker who that pays them to ensure their deal and commission are protected? Having worked with both unscrupulous brokers in both mortgage and real estate sales, I am well aware that many appraisers are bought and paid for, but only after they get the necessary value. Maybe the Zestimate isn’t always accurate, but each and every estimate is accompanied by at least 10, and possibly 50, recent comparables for consumers to make their own educated decision. I may be naïve, but I do not remember the last time an appraiser provided similar support for their subjective, and often bias, value.

2. Kirby on October 28, 2006 11:23 am

   The information provided on Zillow.com IS incomplete and misleading.

   Examples from Zillow.com pertaining to my house:

   1. The Sale History & Tax Info section on Zillow.com for my house shows the 2005 valuation for property tax purposes but only shows the sale price from 2001 when in fact there was another sale in 2003 (3 years ago, more than 2 years before Zillow.com even came into existence). The section then states “No other sale data is available” which isn’t true. The 2003 sale information is available on the county’s website just like the 2001 sale information and the 2005 property tax valuation information.

   2. Zillow.com provides a “Market assessed value” but that value is what the county uses to determine property tax rates and is not a value set by the market. Meanwhile the sale data from 2001 and 2003 — which ARE values set by the market — is ignored.

   Bottom line: The information provided on Zillow.com is incomplete and misleading.

3. David G from Zillow.com on October 28, 2006 1:30 pm

   Kirby -

   There’s a good chance you live in a non-disclosure state — some counties have decided to not make public their sales transactions. In these counties, we cannot calculate a Zestimate - and instead display your tax assessed or market assessed values - which are calculated by your county’s appraiser.

   Sorry for the confusion - you should have seen “Zestimate: None Available” right above the market assessed value.

   For more information about market assessed values and non-disclosure states, you can refer to this post:
   http://www.zillowblog.com/zillow_blog/2006/07/when_is_a_zesti.html

4. DanG on October 28, 2006 4:17 pm

   I’m no expert, but it looks to me as if the NCRC is a classic victim of capture. An org that is set up to help consumers often ends up serving the industry instead.

   Thankfully, there are people working towards making the real estate industry more transparent, instead of protecting those who take advantage of us regular folks. Keep up the good work.

   - A happy user

5. Larry Nusbaum on October 29, 2006 10:02 am

   Zillow is not at all accurate. In the markets that I know and invest in (Bay Area & Phoenix, AZ) it’s useless. Sorry, but I know what I’m talking about.

6. Christianne on October 30, 2006 4:34 am

   You need to have more updated comps and answer your feedback emails. I am a real estate professional and have been checking out Zillow because I know savvy buyers in the DC area where I live and work will be using it as a tool. Your comps are three months out of date. In a rapidly changing market, that’s too much. You need to have a system in place to update comps monthly at a minimum. I would like answers to (1) how often you do upload new comps (provides me with a “relevance” gauge of your data, and (2) what are you doing to make them more frequent?

7. David G from Zillow.com on October 30, 2006 8:29 am

   Christianne -

   As a media publisher, Zillow cannot respond personally to all of the feedback we receive - my apologies. We do however read all the feedback sent to us and use it all to prioritize enhancements to the site.

   We upload newly received sales transactions daily. Those transactions are an average of 3 weeks old; though some are younger and some are older depending on how the county recording and data collecting processes. Sales transaction freshness has improved dramatically since we launched. We now publish new Zestimates (almost) every week — and hope to soon also do that daily.

   If the comps chosen for a house you review are 3 months old, that may indicate there weren’t similar homes sold locally within the past few months or that Zillow failed to identify some recent sales as similar homes. Because choosing comps well is so critical to an accurate estimate, we allow users to refine the list of comps used to calculate an estimate — you’ll find this option in the final step of the estimator tool (click on “create an estimate”).

   We are developing features that will further improve the immediacy with which we learn of sales transactions — just keep watching the site.

8. David Saks on October 30, 2006 12:06 pm

   Zillow is magnificent and is a breath of fresh air to the homeowner trying to get a view of value before the predators get to him. Alan Dalton is a self-aggrandizing, photo opportunist that displays more lard than logic. In Dalton’s mind if Zillow can’t be totally controlled as a marketable commodity in every facet, then it has no purpose. Don’t pay any attention to Dalton. The Federal Trade Commission will support Zillow. I applaud Zillow for giving the tools to those that have been less able to make informed decisions that affect their ecomonic well being and rescue them from the multitudes and clutches of unscrupulous agents and lenders that are more like Robin Hood’s Sheriff of Nottingham Forest than concerned industry professionals. I’m proud to be a real estate professional and proud to have a service as Zilllow available. Zillow is making free, providing a service, that which has been free, and making the work easier for the buyer and seller. Public data ! Public data that unprincipled Realtors engaging in questionable MLS practice and other device use to swindle homeowners, fsbo’s, sellers and buyers for providing. I hope the day will arrive when real estate professionals unanimously recognize the benefit in partnering with the kind of integrity Zillow possesses. Never stop doing good for humankind in such noble fashion, honorable and distinguished Zillow ! With the reversals of the market on our shoulders, and data so important to controlling our economy a vital and essential need for all, Zillow is to real estate what Jonas Salk was to polio.
   A cure….and a gift.

9. Michael on October 30, 2006 1:24 pm

   I like the idea of Zillow.com, and started to keep track of a few MLS listings in my town to see if the Zillow estimate was actually in any way accurate. In February, there was a Townhouse for sale right down the street that had an asking price of 580k, which was right in line with the Zillow estimate at the time (585k). But there were no offers and the price was reduced to 569k about a month later. The price was reduced again around July 4th to 549k. Long story short, after a few more reductions, it did eventually sell for 523k in August. And Zillow does now list that sale, but it says the Value Estimate is 568k. How can the Estimate be 568k when after being on the market for 6 months, and after numerous price reductions, it finally sold for 523k? If something is listed for sale and the price is gradually lowered until someone will buy it, isn’t THAT a pretty accurate indicator of the value? Again, this sale is listed on Zillow, so they have all the data, and still report this lofty value.

   BTW: The address is 4 Fairway Place, 94523, if anyone is intersted it taking a look at what I’m talking about.

10. STEVE JORDAN on October 30, 2006 2:11 pm

    I want to thank Zillow for its Zestimate and Zillow .com. Until Zillow, there was no way of estimating rebuilding or remodeling values, or added values for updating houses. Also the VALUE OF SEEING MANY COMPARABLES, instead of only two or three from an appraiser is very helpful. The real estate industry has many folks that think they are experts in evaluating, real estate, from real estate agents to appraisers. They are just “informed opinions,” to say the least. Zillow makes “informed opinions” of value, based on certain things, just like everyone else does, and its free. Is Zillow 100% accurate? No, but neither is any other opinion, or appraisal for that matter.

    My only negative comment about Zillow is that it is almost impossible to contact any live person at their offices, by phone or email, for anything. Even for advertising on their site.

    We use Zillow every day. We like their “opinion of value” very much,on most properties, and are looking forward to Zillow adding new features to the Zestimate.

    Steve Jordan: President:
    Rebuilding America Inc.

11. Bruce Hahn on October 30, 2006 2:37 pm

    Even though the accuracy of Zillow’s zestimates bear improvement, the concept of providing free valuations is a benefit to consumers.
    Perhaps the best course is for Zillow to post more comprehensive and visible information about the areas where zestimates are least and most accurate while it works to improve the accuracy of its tools.
    Bruce Hahn
    President
    American Homeowners Grassroots Alliance and
    the American Homeowners Foundation

    Serving the interests of the nation’s 75 million homeowners and future homeowners since 1984.

    The American Homeowners Grassroots Alliance is a nonpartisan consumer advocacy organization dedicated to assisting the nation’s 75 million homeowners understand significant policy issues affecting homeowners and homeownership, and empowering homeowners to make their voices heard by state and federal officials.

    The American Homeowners Foundation is an educational and research foundation providing information and tools to help consumers make wiser decisions when they buy, sell, remodel, finance or invest in homes.

    Visit our web site http://www.americanhomeowners.org. Contact us at: 6776 Little Falls Road, Arlington, VA 22213-1213. Direct Dial: 571-214-1013; Headquarters: 703-536-7776 Fax: 703-536-7079.

12. Michael on October 30, 2006 3:32 pm

    RE: Steve Jordan from Rebuilding America Inc, and his comment above.

    I just looked at your website:
    http://www.rebuildingamerica.com/about.htm#

    ..and read where it said, “Americans today face a very serious housing shortage.”

    I’ll just assume that your wabpage hasn’t been updated in a few years. You might be interested to know that most regions’ inventories are up 200% to 400%.

    We’re facing the OPPOSITE of a shortage.

13. Mike Ela on October 30, 2006 4:20 pm

    Hello Lloyd:

    I’m OK with your opening paragraph, and also a fan of Automated Valuation Modeling and Property Risk Analysis, but…I would also like to take the opportunity to respond to some of your comments.
    1) Consumers had access to Automated Valuation Models well before Zestimates appeared in the market. They were available from http://www.homesmartreports.com, and elsewhere in late 2004, and before.
    2) Let make sure everyone understands the median pricing to which you make reference. If your median margin of error is 7.2%, that means almost 50% have an ERROR FACTOR GREATER than “X”, with X being the value. So, 50% of the properties you value are at least 7.2% above/below the market (in which case it seems to follow that sellers are over pricing their homes if they go with your value, or under-pricing their home, and leaving money on the table)? It also means a lot of buyers would be overpaying.
    3) If 62% of your properties are plus or minus 10% of market value as you state, then it stands to reason that 38% of the people relying on your numbers are compounding the error in item 2 because the error factor is greater than 10%, correct?
    4) You say you do this “by looking at millions of transactions and Zestimates –that’s millions of comparisons, not by picking a handful of examples and drawing conclusions that make us look good”. Trying to overwhelm and impress everyone with the brute strength of all your numbers? Seems like that’s “trying to look good”. How does looking at millions of transactions help a person trying to value their home in Anytown, USA? If there are only 20 home sales in Anytown, do you use those 20 home sales or “Millions”? If you use those 20, why say “millions”? If you’re using millions, what good is the value estimate for Anytown? Real estate values are largely determined by what’s happening in a local real estate market, not by reviewing millions of transactions all over the country. Also, if you are re-using Zestimates (or are you just looking at them, and if you are just looking, what good are they?), and 38% are more than 10% (OR GREATER) from the values used to create your Zestimate, won’t the result be that much less accurate? I think you’ll find that to be the case in a statistical sense.
    5) As to opening up your database for anyone to input values, I’m not sure where the value lies here. How do you know they are correct? Are you also relying on these numbers, plus sales transactions, plus your stated inaccuracies of Zestimates (the 38% to which you alluded) in your own value calculations to then re-apply to your calculation engine to generate values? It seems that this will compound the inaccuracy of your calculations. You’ve also clearly stated to the real estate industry that Zillow’s revenue model is strictly an advertising model. So, are you doing these things to get more eyeballs looking at your website (for advertising revenue), or do you truly rely on them to improve accuracy of your estimates? If the latter, how do you validate the information?

    It’s good to have dialog with NCRC and others so long as it is truly for the purpose of offering better estimates as opposed to just attracting attention to Zillow. I’m a fan of better estimates for consumers and investors, with a big dose of risk analysis to really understand a local market.

14. Sonia on October 30, 2006 4:23 pm

    I received an email from a client I am working with who was interested in putting an offer in on a house with 2.5 acres of land. He sent me the Zillow valuation and asked why the house was valued so low ($150,000 less than asking price). When I looked at the comparables, I saw why. Almost every house used as a comp had only .14, .16, or .18 of an acre of land. Nowhere near the amount of land of the subject property, therefore not comparable at all. Yet there were several comparables available with 2-3 acres and similar homes to the subject property.
    When I looked up my own house, which is a waterfront with gulf access single family home on a half acre lot, the Zillow comps included: A nonwaterfront house on a busy street that includes commercial properties and nonwaterfront townhomes on virtually no land. Again, there were several comparable homes available that were actually on the water.
    As a real estate professional, I am used to compiling market analyses and scrutinizing ‘comparables’. The average consumer may not do that because they are led to believe Zillow is accurate or within a percentage of accuracy when it is frequently grossly inaccurate.

15. 1000 Flowers Bloom on October 30, 2006 5:13 pm

    Real Estate Industry Fights Back Against Zillow

    It’s funny how established industries fight back with lawyers and the government against new upstarts. First it was the music industry and now it’s real estate… A good example is the complaint that was lodged against Zillow to the FTC

16. Chris Crocker on October 30, 2006 5:13 pm

    Loud Voice coming from sound system… “Pay no attention to the man behind the curtain” (Wizard of Oz). Most of the people who don’t like Zillow fear the impact of transparancy on their ability to generate revenue. Zillow isn’t going away (your customers LOVE them), you have two options. 1) Lower the price of your service or 2) increase the value and transparency to your clients.
    Simple.

17. David G from Zillow.com on October 30, 2006 5:23 pm

    Bruce -

    Is this what you were suggesting? (scroll down the page and click on states to see each county’s accuracy) http://www.zillow.com/howto/DataCoverageZestimateAccuracy.htm

    Michael -

    Good example of a difficult house to Zestimate — golf course developments are a real challenge (I’d love to hear a Realtor’s opinion on this topic). Usually I hear from the guy with the view of the 18th (whose house is worth more) but this time it is the home at the (busy) entrance (that’s worth less).

    We don’t go back and retroactively “correct” Zestimates when we hear of sales — this lets you take historic Zestimate accuracy into account when evaluating your Zestimate. This house’s Zestimate has however responded to the news of the sale. Most importantly, note that the sale you quote was well within Zillow’s value range - a concept I explained further in this here:
    http://www.zillowblog.com/zillow_blog/2006/05/home_in_the_ran.html

    Mike -

    If Anytown, USA only has 20 homes, we will have insufficient data and will not calculate a Zestimate. For more on when we don’t Zestimate, read this post:
    http://www.zillowblog.com/zillow_blog/2006/07/when_is_a_zesti.html

    Where we do calculate Zestimates, we measure and report accuracy locally, using only local transactions. See my reply to Bruce (above).

    We validate owner-contributed information by requiring that they prove and warrant their ownership — and then we trust them — but give visitors the ability to “flag” content for our review. Owner-contributed data does not impact Zestimates but it may someday — we are very encouraged by the participation we’ve had from owners. As to why we did it … there are a lot of good reasons … but the reason we made it a priority is that our users asked us for it as you’ll see if you review this feedback we published just after our launch:
    http://www.zillowblog.com/zillow_blog/2006/02/what_zillow_use.html

18. olivier on October 30, 2006 6:43 pm

    Some of the valuations on zillow are accurate; some of the valuations are very much inaccurate.

    I think it is an OK indicator of trends, but the data is often wrong; i see many case where the last sale price is wrong; house improvements are not accounted for; certain details which make/break a house price in my area (e.g. closeness to certain busy roads) are absolutely not accounted for, improvements are not accounted for.. so..in some respect it is excatly as useful as the county assesment i receive every year: Useless.

    My advice to zillow is to adequaltely use the million of potential users to adjust their valuation locally. Because on a macro level, Zillow really does not work.

19. David G from Zillow.com on October 30, 2006 7:51 pm

    Olivier -

    Great suggestion! That’s exactly what we’ve done; owners now publish their updated home facts and customized estimates on Zillow.com.

    To check out these new features, search for your house on Zillow, click the address on top of the map to get to the details page — there are now buttons just below the Zestimate — one is to “Owners Tools”, which presents you with the options of claiming your home, editing your home facts and creating an estimate (and making it public).

    Thousands of owners now claim their homes daily — many of them are setting the record straight and publishing the current and complete facts about their house. Some have calculated refined estimates and published those.

20. Mike D. on October 31, 2006 8:56 am

    If they say Zillow is liable for inaccurate data, then all real agents, brokers, appraisers and those AVM companies are liable too.

    Aren’t they all provide either free or paid home valuations? Aren’t they all include a disclaimer on their data? Can any of them guarantee accuracy? Aren’t they all provide estimates or opinion of value?

    Why are you singling out Zillow?

21. Greg Tracy on October 31, 2006 5:28 pm

    Is it possible that a company can actually develop a model that is all about empowering the consumer, without trying to cut the agent out of the deal or create complete anarchy within the comfortable confines of the real estate community?

    Not according to many.

    There are some of us who believe that providing the consumer tools can be a good thing, even if those tools hint of our own.

22. Kirby on October 31, 2006 8:14 pm

    David G —

    1. I live in GA which is not a non-disclosure state according to the link you provided.

    2. As I stated in my earlier comment, the county DOES provide sales information on their website for the public to see (in the same place as the assessed value used by the county for property tax calculations and reported by Zillow.com) — why doesn’t Zillow.com?

    3. I looked up a house that a relative sold in November 2005. You don’t have a Zestimate for that property either but you provide a “market assessed value” of $428,400 even though you show the November 2005 sale price as $480,000 on the same page! So you ignore the recent actual market value and provide a “market assessed value”.

    Again, the bottom line is that the information provided on Zillow.com is incomplete and misleading.

23. David G from Zillow.com on November 1, 2006 7:10 am

    Hi Kirby,

    Thanks for the additional information.

    We don’t have data coverage for the entire country yet but are working on it — Georgia’s a high priority for us.

    Your home facts and sales records originate from two different sources so it’s possible that we’d have one set of information and not the other (in some areas). Zillow uses data providers who collect and aggregate assessor and recorder data for us — we don’t collect this information directly from the counties. In your county, our vendor simply hasn’t collected enough transactions yet for Zillow to be able to calculate a Zestimate.

    When our data is incomplete, we’d rather not make wild guesses about estimates. In these scenarios, we display the tax assessed or appraised (market) value and don’t calculate a Zestimate.

    The Zestimate accuracy table also displays data completeness for all states and counties:
    http://www.zillow.com/howto/DataCoverageZestimateAccuracy.htm

24. Steve Oshins on November 4, 2006 6:50 pm

    After several unsuccessful attempts to get Zillow to fix it valuation of my home, its clear that the people at Zillow don’t care about fixing their errors. My house is worth at a minimum $3.5 million and is probably more in the $4.5 to $6 million range. Zillow hasn’t recognized that I combined two lots into one a year and a half ago, so they have my main house and lot at $863,000 and my adjoining lot at $518,000. Since they clearly have the old lot numbers, their formula is counting my property tax info as $0 in 2006 even though it’s actually about $35,000. Therefore, they are incredibly wrong which has not only done this to my house, but has brought the $4 million houses in my neighborhood down to $3.0 to $3.5 million since my house screws up all the comps. Zillow either needs to fix their problems or put a huge disclaimer on their site. But to ignore my emails several times over the past year even though I keep giving them my new parcel number (which was changed about 18 months ago) they are telling all of us that their valuations are misleading and unhelpful. Zillow - Either fix my house Zestimate (2800 High Sail Ct., Las Vegas, NV 89117) or put a valid disclaimer on your site saying that you don’t care about your accuracy and that emails from homeowners will not be acted upon by your staff.

25. David G from Zillow.com on November 6, 2006 10:37 am

    Hi Steve,

    I apologize and understand your frustration. Your house’s Zestimate actually did get our attention and has highlighted a few challenges we need solutions for. We are working on two initiatives that would solve the Zestimate problem for your house — one is to further improve the way we scrub tax assessment information before it is imported to our database and the other will allow our staff to make manual corrections to the Zillow database. Both fixes are however a few months away from deployment.

    Today, raw data is imported daily from our data providers — so, while our vendor is still receiving incorrect information from Clark County, your Zestimate will remain inaccurate. I am sorry for that.

    I notice that Clark County has correctly assessed the 2007 property taxes for your house. When that tax roll is published and passed on to our data providers, your Zestimate will also correct itself.

    I am sorry for not clearly communicating these challenges. It’s great to see that you’ve claimed your house on Zillow and published an updated estimate. Owners know their properties even better than local governments do — we are also working towards having the Zestimate itself rely primarily on the owner’s facts.

    Thanks for your patience.

26. Steve Oshins on November 6, 2006 9:43 pm

    David-

    Thanks for the reply. I’ll see if it gets fixed in a few months. I have a few suggestions. Firs, I don’t think it’s a good idea to use the owner’s facts change the Zestimate since that ultimately will lead to people invlating their information which takes away Zillow’s independence. Second, I suggest that your Zestimate formula be designed to automatically replace variables that seem outrageous, such as my property showing a $0 property tax in 2006. I would suggest that if a variable is out of whck by some statistically significant percentage, the formula should look at similar properties in the area and use their mean figure in place of the out of whack number. That would fairly get rid of many problems associated with incorrect data and would smooth out the data and would reduce the number of posts from mad people like me. What do you think?

27. David G from Zillow.com on November 8, 2006 3:38 pm

    Steve -

    Thanks again for your patience! Good suggestions;
    - You are right about the need to scrub the raw data before using it to calculate Zestimates. We already have a bunch of these data cleansing rules in place and will be adding this one and a few more when we make the algorithm upgrades in Q1 ‘07.

    - We don’t use owners’ data in calculating Zestimates today but we are considering it — and we will only do so if our analysis shows that this improves accuracy. I have been monitoring the way owners use this feature and must say, I’m pleasantly surprised that the vast majority are not inflating the facts about their homes. Our Zestimate algorithm also works in such a way that it effectively ignores other Zestimates — so; should a homeowner be able to inflate the value by updating their home facts, that error would not impact other Zestimates.

28. Smithy on November 10, 2006 10:30 am

    Zillow has become the coined word for inaccurate in our office. For example, if we don’t have enough information to make estimates for project dates, we just make the best guess we can and call it a zillow estimate. No one has much faith in a zillow estimate.

29. Joel S. on November 12, 2006 7:24 pm

    My house (13399 N. Regulation, Oro Valley, AZ) is appraised for over $540,000. The Zillow estimate is only about $300,000+. The comps you use are not on my street or even in my neighborhood!!! This is very inaccurate and needs to be corrected. You are affecting many people. Please either correct your valuation method or state that this house has no comps that are relevant.
    Thanks and please let me know when this will be corrected.

    Joel.

30. Lee Ovington on November 14, 2006 8:28 am

    The issue that most seem to be missing is that Zillow is reporting a “median” error margin as an indication of accuracy. This is possibly a misleading measurement for accuracy. The mean error margin would probably be a better indication of Zillow’s accuracy. Why not report it?

    http://valuation411.blogspot.com/2006/11/im-no-william-tell-but.html

31. David G from Zillow.com on November 14, 2006 8:43 am

    Joel -

    You should notice that hour home’s Zestimate is quickly correcting itself - it just increased by $60K and should continue to do so over the coming months so as it climbs into the region of the January sales value.

    It’s surprising that your home only recently started appearing in our search results and that we only started calculating its Zestimate in September ‘06 (as you can see in the Zestimate graph) — we’re not sure why that is and are investigating this case further. Thank you for your feedback.

32. Me on November 14, 2006 8:50 am

    Zillow does not provide any transaction details (arms length, trustee sales, Estate, divorce), no condition assessment, no style/location indicators, no indication of concessions, no indication if personal property is included or not in price, no indication of size calcultion (total sf vs. above grade), no indication of the lower level finish if included in SF, and foreclosure/fraud/flip stats for the area–these, among others, are critical to understanding value. An algorithm is great for counting apples and predicting future apple growth among known variables–not for housing price/values.

    Zillow is purely guessing, with data that looks like swiss cheese. The final number given is really a “Guesstimate”, not Zestimate. People, please use your brains.

33. Roberta Bray on November 14, 2006 11:32 am

    I find it hard to believe that you would make comparable homes as you have done with mine. You listed 9 other homes none with the same sq. footage, by different builders with different size lots and in different locations on the streets in my neighborhood while there are at least 6 or more houses that are identical to my house by the same builder, identical floor plan and sq. footage and in similar locations on the street. You have reduced the value of my home by $40,000 in the last 6 months and kept a reasonable change in all the others that are identical, including one house that is immediately accross the street, two on the next street both ways, all on the corners with the same sq. footage and similar property sizes. My house is in no way run down or unimproved.
    Comparing Apples and Apples instead of apples and oranges makes more sense. How can the ones you chose as comps be fair to me and my property value? Most of the identical houses have been sold and the fact that I have not should not decrease my property value any more than their property value. In some cases their property value has increased while they have done nothing to improve their house, and my property value, according to your site, has plummetted while doing nothing to decrease the value.

34. David G from Zillow.com on November 15, 2006 12:11 pm

    ME (AT 8:50) -

    Zillow excludes transactions that are not clean full-price sales. The public record is typically accurate in that regard but we also screen sales data for outliers (based on value) in the remainder of transactions in case any have been incorrectly categorized. Regarding square feet; all finished sq.ft. is typically included in our calculation but rather than do the math (the area of individual floors is often omitted from public records), we’re using the value the county passes us for total finished sq. ft. This and the other house attributes are defined for owners - just click on the attribute name in the process for editing house facts.

    Estimating house values is not easy for the reasons you mention and for many others; and our algorithms are becoming increasingly aware of these complexities. Thanks for your feedback — I hope this explanation addresses your concerns.

    Roberta -

    I’m sorry that you’re not satisfied with your house’s Zestimate. Picking great comps is difficult without having visited your house. That is why we’ve created a tool for you to recalculate an estimated value by choosing better comps. This is done in the 4th step of the My Estimator tool on Zillow, which is described here:
    http://www.zillow.com/howto/MyZestimator.htm?pagenum=4

    Note that if you have claimed your home, you also have the option to publish your updated estimate (with comments) — which will then appear at the top of your homes details page. Instructions for claiming your home can be found here;
    http://www.zillow.com/howto/ConfirmingOwnership.htm

35. Real Estate Owner on November 18, 2006 9:53 pm

    Real Estate Owner

    An en-bloc sale may bring a windfall to property owners on They then contact a mortgage type FSBO listed on 10/24/2006 - 3/2 Cozy Home - Re

36. Allen on November 20, 2006 1:01 pm

    When was the last time you could use Zillow to close on your home loan? Right….so why is everyone so bitchy about what they say. Want to know what your house really is worth…consult your local property appraiser….oh by the way, if you call 3 appraisers, guarantee all 3 of them give you a different value! As a licensed mortgage broker, I use Zillow only for pre-limenary research…correct address, tax info, and I use the local comps to get a “ball-park” idea of value. From there I consult my appraisers and go from there. Some of you out there need to try that route.

37. Barbara on December 5, 2006 7:31 am

    My home is one of the ones with the incorrect data. So last month due to only having “2″ baths (in reality I have 3) my home dropped over $6000. Wow Thanks a lot as I am selling as a FSBO. Perhaps if someone who is looking at my home bothers to put in the correct info they may get a better comparable, but will they do it? I did correct it, but I think you now have it way over. So no happy medium for me. I do wonder how many possible sales on this property I lost due to your data? Not a happy customer here and forced to participate unwillingly.

38. David G from Zillow.com on December 5, 2006 11:06 am

    Barbara -

    The data in question is actually the public property records for your house. If they are incorrect, that information will have to be corrected with your county before the public record reflects the accurate attributes for your house on Zillow and elsewhere. Because public records can be incorrect, Zillow lets owners publish updated facts along side the public record on our website. To edit you home’s facts on Zillow, follow these steps:
    http://www.zillow.com/howto/EditingHomeFacts.htm

39. Jason on January 5, 2007 8:03 am

    I own the house on 305 Clayton Road in Chapel Hill, NC. I have claimed the house and changed some facts that I noted were incorrect but I couldn’t fix the huge flaw in the sales history. It says that the house was sold on 8/16/04 for $91,000. I wish! The actual purchase price was $455,000. I believe what happened is that the county’s information regarding sales price shows 910,000 and to get the sales price you have to divide by 2. Looks like the person who entered the data just truncated a zero. Zillow is showing other recent sales history on my street correctly so this seems to be a fairly isolated problem. How do I fix it?

40. kobbe on February 17, 2007 7:53 pm

    I use zillow very often and I am very pleased that there is such useful tool to estimate home market value as close as it could be. I just want to express my appreciation for the work and efforts that has been put into this complicated market. I believe it is priceless tool. Thank you.

41. LM on February 28, 2007 7:34 am

    Zillow needs to learn a few database calls..
    I ‘zestimated’ my home(don’t you hate cutesy web terms?) and found that there was no way to sort waterfront from non-waterfront lots in the comparable values zillow averages. Que? Waterfront is listed on the public real estate records. They can’t figure out how to call the db?
    One of their ‘comps’ also included a house which was sold for $3 (three dollars) per sq. ft., which was given the same weight in their price average as homes selling for between $175 per sq. ft. to $395 per sq. ft. Three dollars per sq. ft. is the price your Mom and Dad sell you a house for, not an accurate reflection of current market value. Doesn’t a per sq. ft. price so outside the norm ring a few bells for these people?
    Puhleeese…

42. Mike on March 4, 2007 6:18 am

    I want to express my appreciation for the free service Zillow offers to the public. I especially love the ‘heat map’ for a broad over view of values to help narrow neighborhood locations. One thing I think would even help that more is a ‘crime heat map.’
    Just wanted to put in my two cents. Zillow is leaps and bounds more helpful than scrolling through a long list of houses in the MLS.

43. Carlos Paviolo on March 25, 2007 9:27 pm

    I am comparing the price of my condo with those of my neighbors and my unit comes 6% under any value of similar condos in our complex. When we bought our house, a similar unit in the complex sold at a lower price and now is valued 7% more than ours.
    Being my unit the only one with a view, I am wondering if my first name affects the “Zillow Algorithm” negatively. I do not see any other explanation.

44. David G from Zillow.com on March 26, 2007 10:43 am

    CARLOS —

    I can guarantee you that your first name has absolutely no bearing on your condo’s Zestimate value. Owners’ demographic information is not an input to the Zestimate algorithm and it’s not a part of our database.

    A Zestimate value is a starting point in calculating the value of a home — it’s an estimate based on the public records we have for your house. The accuracy of Zestimate values varies according to the quality of the data we have about your house and that of the surrounding neighborhoods.

    The 6% difference you mention is not very significant — it could be caused by just a 3% variance in the Zestimate value of both properties (if one were high and the other low). If you’d like to send me your address [davidg at zillow dot com] I’ll look into this in more detail for you but I also recommend you read this earlier post that discusses varying perceptions and expectations of Zestimate accuracy; http://www.zillowblog.com/zillow_blog/2006/08/your_very_far_i.html

45. Mark Crane on April 27, 2007 12:53 pm

    POINT 1:I live in a California neighborhood and 30 percent variations in Zestimates of identical homes just doors apart are obviously based on nothing more than county tax assesments, for which CA has peculiar rules.

    POINT 2: There is absolutely no getting around it — people believe zestimates when considering a purchase.

    FINAL POINT: The problem with Zillow is only that it tries to do something for free that actually costs a bit. Accuracy and public acceptance could be greatly enhanced and the mission nearly perfectly fulfilled if only they would charge a nominal fee and do a bit more work. People like myself whose homes are zestimated badly stand to lose 10’s or 100’s of thousands because of zillow. Zillow ’s contant reminders of its legality and its good intentions are not helping its reputation. Zillow needs to add fee services and to use the extra doe to fix the problems.

46. Nilanjan on May 16, 2007 6:32 pm

    My home is being shown at $585K. My next door house with exactly same plan and similar upgrades is shown at $637K (+9%). Next door from that, same plan is $669K (+14%). It’s stupid. This is harming my home which is up for sale. Worst part is even if I include nearby comps, it only corrects the price a little bit, about 3%. There’s no way to ask zillow to correct it. This is voluntarily misleading consumers, and 10-15% price difference means a lot to me. You cannot get away posting a disclaimer since you are a large institution now and lot of people bank on the estimates and think they are correct. It’s like the airlines company putting disclaimer that the plane might go to any destination it chooses. It doesn’t make sense!

47. MaraBlue on June 3, 2007 1:37 pm

    Zillow *seemed* to be accurate last year, based on current market values and a real life appraisal of my house. Now suddenly it’s totally out of whack and ALL over the board, being $100-200k OFF. That’s a HUGE “margin for error.”

    My house appraised 3 months ago for $310k, in a neighborhood where $350-400k is typical for like-sized or conditioned houses.

    Today Zillow states my house is valued at $263k, claiming a drop of $17k in the last month. I understand market values fluctuate, and I knew there’s been a downturn, so this wasn’t exactly a surprise to see.

    What IS a surprise (and has pissed me off to the point of spitting nails towards Zillow) is that they don’t seemed to be taking neighborhood comps into account. In fact, the figures seem to be just pulled out of….the air. Or somewhere else (use your imagination here).

    My lot is one of the largest in the neighborhood, at .16/acre (the city records claim .18). I have a 2 car garage and recently remodeled with many major upgrades. I don’t expect Zillow to “know” about the upgrades, but just based on the lot size, sq footage and know factors, their figures are totally out of whack.

    3 other houses adjacent to mine are for sale. One is a teeny, tiny older house on a .10/acre lot (it looks drastically smaller than that), no garage, and facing the railroad tracks. Somehow Zillow listed THAT house’s value as $345k, with the land being valued at $100k. MY land assessed value? $35k. Where do you come UP with these figures? This isn’t what my property tax statement claims.

    That little house next to me, Zillow-valued at $345k? It just sold for $178k. I could see $10k, 20k, maybe even a 30k discrepancy…but when you start getting into the $100k-200k differences….

    Have you seen that “Ask.com” commercial, where the little boy asks his dad if he uses a “lame algorithm”? Zillow definitely HAS a lame algorithm.

    The problem is, you’re messing with people’s homes, the biggest investment most people will ever make. Those of us who have lived in the same house for 7-10 years also seem to be hurt by your lame algorithm. I suggest you fix it…or Arizona won’t be the only state you’re banned from.

48. D.R. MENDEZ on February 15, 2008 8:51 am

    MY HOME IS ON WRONG STATE ALTOGETHER !!!!!

49. Bill M on February 15, 2008 11:15 am

    Can’t seem to get accepted on the sign in-???

50. David G from Zillow.com on February 15, 2008 7:24 pm

    Bill -

    Please comment again using the email address you’re trying to register (it’s not published) and I’ll look into it.

51. Carol S on June 3, 2008 3:34 pm

    We fell victims to the mortgage broker’s bait and switch at closing last summer (given a subprime interest only for 10 yrs. at closing when promised 30 yr. fixed). We were told that we could refinance, as our house appraised at 80k more than we paid.

    Today, the same appraiser assures us the house is worth at least the same, but she found comps in the same type of neighborhood nearby at 65k more. It is a very nicely manicured neighborhood on a hill above a much lower priced neighborhood. More expensive homes are on the hills behind us. For that reason, our neighborhood is one of a few in the San Diego area that has held/increased value.

    UNFORTUNATELY, Wells Fargo, my lender, insisted on doing a desktop ZILLOW appraisal which pulls on the much smaller, older homes and far less desireable neighborhood in the valley. They have written off all parts of San Diego as a “depressed market,” therefore they won’t refinance us out of our subprime loan, and they have no interest in doing a “real” appraisal.

    ZILLOW does NOT take into account neighborhood, location, and desirability. It merely makes a square foot for square foot comparison with sales in a set radius. RIDICULOUS! According to Zillow, my property never was worth the $650k it appraised at, so the numbers have never been accurate. Zillow takes the lowest comps and runs with it.

52. David Gibbons on June 3, 2008 4:04 pm

    Carol - a lender cannot (grant or) deny you a loan based on a Zestimate value. If you believe that that’s what they’ve done I’d be glad to get on the phone with you and your lender and set them straight (my e-mail address is davidg AT zillow DOTCOM.)

    It’s more likely that your lender simply referred you to Zillow to backup their opinion and it’s highly unlikely that they’re using Zillow to make their determination on depressed markets. A big bank like Wells Fargo will typically have multiple commercial AVM’s (Automated Valuation Models) for that purpose.

    Also note: Zillow definitely does take location into account when calculating Zestimate values and we do not “select the lowest comps” - Zestimates aren’t calculated by picking comps but rather by analyzing the sales trends of all recent sales in your area.