Last time, you’ll remember, I discussed development of a statistical model that produced a much better estimator of property value in Wilton Manors than the cruder method “price per square foot”. The multi-factor model did include price per foot as one of the inputs, but also included several other statistically significant variables.

Astute, knowledgeable readers (i.e., all of you) will rightly ask, “Does it work? Is it better? And by how much?”

I applied my model to all 67 single family home listings active in the Multiple Listing Service database as of this morning (June 30th). I compared the output for each property to the current listing price. By comparison, I also looked at the market value as stated by the Broward County Property Appraiser, and also considered information from the Zillow real estate portal (in common use among the public).

The results are in the graphic included here, but require explanation.

The current average list price for a single family home in the Island City is $604,000. My model – without even a drive-by or peek in the windows or yard – comes up with an average value (sale price) of $588,000. That’s just over 97 percent of list price. (I think that’s pretty good, frankly.)

The “market value” from the property appraiser averages to $418,000 – 69 percent of list price. This may not seem very good. However, it’s a readily available number, developed (presumably) by people with knowledge of the local market. So, if you are trying to value a property not currently on the market and not sold recently, it can give you a quick ballpark number – just multiply by 1.45.

You will note two Zillow numbers. The first number is the average of the current Zestimates on the MLS-listed properties, which turns out to be $582,000 – a bit lower than mine but at just over 96 percent of list, it’s not bad.

But I don’t think that’s the relevant measure to use to assess the value of the Zestimate. If a Realtor lists a property, there is some degree of evaluation of the current market, property condition, recent sales and such to set a list price. It wouldn’t require a great deal of analytics to take 96 percent of a list price and use that as a value estimator – especially since state and local Realtor boards frequently publish statistics comparing sales prices to list prices.

The problem comes when you’re trying to value a property that is not listed for sale. Helpfully, Zillow provides the Zestimate history for us (thanks, Zillow). If you consider what the Zestimate was right before the home was listed, you get an average value of $465,000 – 77 percent of list price! This would compare with my model’s estimator of 97 percent.

Now, of course, Zillow has a great website, provides many other features and value, and calculates the Zestimate for millions of properties, not just those in Our Fair Island City. Yet an enterprising geekish entrepreneur might consider regional application of more-robust models. For starters.

James Oaksun, Florida's Real Estate Geek(SM), is Broker-Owner of New Realty Concepts in Fort Lauderdale. In addition to having degrees from Dartmouth and Cornell, he is a Graduate of the Realtor Institute (GRI).