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in census tracts citywide.
As mentioned above, we used GIS techniques to measure the distance from each
sale in our database to all Nehemiah and Partnership sites. 12 Then we effectively created
rings around each project to determine whether the prices of properties in the rings
surrounding the developments were affected by their proximity to these new
homeownership developments. To give a sense of these rings, Figure 5 shows an example
of a Partnership development located on the Brooklyn/Queens border and its surrounding
rings. The innermost ring extends 500 feet (usually one to two blocks) from the project;
the second ring extends 1,000 feet (one to four blocks), and the outermost ring extends
2,000 feet (three to eight blocks).
Figure 5
Partnership Development on Brooklyn/Queens Border
Park
Cemetery
12 Since all buildings in New York City have been geocoded by the New York City Department of City
Planning, we used a “cross-walk” (the “Geosupport File”) which associates each tax lot with an x,y
coordinate (i.e., latitude, longitude, using the U.S. State Plane 1927 projection), police precinct, community
district, and census tract. A tax lot is usually a building and is an identifier available to the homes sales and
RPAD data. We are able to assign x,y coordinates and other geographic variables to over 98 percent of the
repeat sales using this method. For the Nehemiah and Partnership data, only the tax block on which the
property is located (which corresponds to a physical block) is available. After collapsing the Geosupport
file to the tax block level (i.e., calculating the center of each block), we were able to assign an x,y
coordinate to 99.7 percent of these projects.
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