[oneweirdtrick]

I never thought of Zillow being the bigger company until I compared their listings to Trulia's. Looks like Zillow has been acquiring other real estate sites like crazy over the past few years to get to where they are now. Pretty impressive. However I feel like the Zestimates are still not very accurate. Not even sure how they get those estimates. Can anyone shed some light on this?

Also, I wonder how long it will be until Amazon acquires Zillow and 'homes' will be listed in departments.

[nostromo]

Zestimates are worse than random. There seems to be no sanity-checks in the algo whatsoever.

Check out this Baltimore home. In a single month it's estimate went from $700k to $300k, then back to over $700k during the worst part of the housing slump, and back down to $300k during the recovery. lol wut?

http://weblogs.baltimoresun.com/business/realestate/blog/Zil...

[brucehart]

I did an analysis on the accurate of Zestimates a few years ago. I took sales data for my county from the previous month (that Zillow had not imported yet) and compared it to the Zestimates Zillow computed. The mean error was almost 0, but the standard deviation was about 20%. An engineer from Zillow wrote to me and said my analysis was close to their own internal measurements. Their algorithms might have improved since then since it sounded like it was something they were continuously trying to improve.

[Kamic]

do you have a link to that analysis?

[brucehart]

It was on my old blog which is no longer online. I'll see if I can find the article in my backups and post it somewhere. I should probably do the analysis again since my original test was during the end of the housing bubble when prices were unstable.

[encoderer]

As far as number of listings of on-market homes, Zillow and Trulia are certainly very close to one another. Possibly in your local market that wasn't the case, but generally speaking it is.

At Trulia, we also calculate Estimates for properties but in most cases we do not show that data. In theory, the estimates work much the same way an appraisal works: Comparing the home on its various attributes to recent sold homes nearby. Obviously it's not possible to capture the essence of an Appraiser in an algorithm, but we display the estimates in cases where we feel it's better than just showing an old, out-dated last sale price.

[wpietri]

I expect Amazon will stay the hell away from that market. Note that they haven't even gone after cars, which are a much easier thing to sell.

Homes are a mess: novice buyers and sellers, complicated laws, tricky financial deals, and a "product" that is complex, unique, and can have many hidden flaws. Real estate agents frequently get sued when things go wrong [1] [2]. The last thing Amazon needs is to get in the middle of that.

[1] http://www.risceo.com/10%20Most%20Frequently%20Made%20Claims...

[2] http://www.jdsupra.com/legalnews/emerging-trends-in-lawsuits...

[fragmede]

> Note that they haven't even gone after cars,

Buy a Nissan Versa Note: http://www.amazon.com/gp/feature.html?docId=1001359341

I really wanted to put my affiliate ID on that link ;)

[wpietri]

Interesting! What's the story with that? It's not a real product link, and you can't search for the product. Some sort of marketing stunt?

[clauretano]

Regarding how Zestimates are calculated, see http://www.zillow.com/zestimate/ --a lot of high level explanation there.