Department of Numbers

NYC Home Price Comparison

Posted Tuesday, December 08 2009

I thought I'd post some initial comparisons of Department of Numbers median prices with industry price data. Corcoran, the largest residential real estate brokerage in New York, publishes a quarterly review of pricing for Manhattan and Brooklyn as well as some prominent neighborhoods. It's quite nice actually, and I encourage you to check out their reports. The guides also serve as a good starting point for comparing Department of Numbers pricing.

Corcoran looks at median and average apartment prices in New York in a variety of ways, but it's not always clear what the full underlying methodology is. For instance, they report average and median prices for Market Wide - All Apartments in Manhattan and Brooklyn. I'm assuming "All Apartments" includes cooperatives and condos, but I'm not exactly sure what property types (if any) they include beyond that. Do they include house sales? What about multi-unit sales? In the end I decided that looking at DoN's metrics for all homes and apartments was the best comparison for now. It's a little apples and oranges, but not wildly so. Here are the results for Q3 2008 and 2009.

Corcoran Quarterly Apartment Prices Compared to DoN Prices for "All Apartments"

Reporting Borough 2008-Q3 2009-Q3 Year/Year
Corcoran Manhattan $971,000 $799,000 -17.71%
Department of Numbers Manhattan $875,000 $775,619 -11.36%
Corcoran Brooklyn $480,000 $465,000 -3.13%
Department of Numbers Brooklyn $504,981 $470,000 -6.93%

This is really quite good considering we don't know the exact details of how Corcoran calculates their median prices. I plan on publishing something on DoN's methodology soon with the hopes of getting feedback that might enable me to refine the filtering process and perhaps improve the comparison. Having said that, the goal here isn't to recreate some other index. I'm trying to build a well defined, timely and independent index that New Yorkers can use to get a better look at monthly aggregate real estate prices. It will necessarily be an iterative process.