Why Zillow is a “No-Go” in San Carlos.

January 25, 2008

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Zillow.com is a popular website for many potential home buyers and sellers. And why not? For buyers, it utilizes a cool Google-like satellite-hybrid map that allows you to search cities or particular neighborhoods for homes that are for sale. It even puts together comparable sales data for specific home sizes. For sellers, you can use the very popular “Zestimates” feature to give you an estimate of what your home is worth. Sounds great, right? It is, except for one minor detail — the accuracy of the information you get out of this site is questionable at best.

Allow me to explain. First, from my days as an engineer, we abided by the GIGO (Garbage-In, Garbage Out) Law. This “law” simple states that no matter how solid your algorithm is, if you plug garbage data into it, you're going to get garbage data out. It's obviously a little tongue-in-cheek, but it really applies here.

Let me provide you with a live example to prove my point. Saint Francis Way is a very nice street in White Oaks — lots of nice homes, great schools, everyone wants to live there. I punch up Saint Francis Way on Zillow, and bingo! I am thrilled to see that there are no fewer than 3 homes for sale right now on the most desirable blocks — Eureka! Pack the bags, honey!

Those addresses on Saint Francis that show “for sale”in Zillow are:

  • 1972 – 3BR/2BA $1,249,000
  • 1924 – 3BR/2BA $1,198,000
  • 2424 – 3BR/1BA $949,00

Good so far? But here's the problem — not one of these homes is actually for sale. Here's the real status of the three:

  • 1972 – Sold on 11/15/07 for $1,235,000. (2+ month-old data)
  • 1924 – Sold on 12/29/07 for $1,175,000 (1 month-old data)
  • 2424 — Pending sale since 1/15/08. (2 week old-data)

You can repeat this exercise on Howard Ave, Eaton Ave, and other streets in San Carlos, and you'll get similar results. Am I just being nit-picky on details? Maybe…but if you now take this data above and try to do something useful with it, like running comps or estimating what your home might be worth, you can see where the wheels fall off this wagon very quickly. Data that hasn't been updated in two months is useless in a real estate market as dynamic as San Carlos.

Why doesn't Zillow have accurate or updated info? I don't know — it's all readily available data. But what I do know is that if you plug garbage in…well, you get the idea.

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