Through its Philadelphia Green initiative, the Pennsylvania Horticultural Society (PHS) has cleaned, greened, and improved nearly nine million square feet of vacant land. PHS wanted to understand the program’s impact on property values and neighborhood redevelopment throughout the city.
Client: The Pennsylvania Horticultural Society
Challenge: After nearly 30 years of transforming trash-strewn vacant lots into attractive green spaces, the staff at PHS have a large collection of stories about the positive impact of land stabilization: increased feelings of safety; more interaction among neighbors; an uptick in sales of vacant lots. Several recent academic studies support this anecdotal information, most notably an econometric analysis from Penn’s Wharton School that identified a significant increase the value of properties adjacent to cleaned and greened vacant lots. PHS wanted to extend these studies and try to quantify how the Philadelphia Green program might be contributing to neighborhood redevelopment throughout the city.
Solution: PHS worked with Azavea to develop research questions: What is the relationship between cleaning and greening efforts and sales of vacant lots? How does this relationship vary from neighborhood to neighborhood? Azavea assembled several large data sets, including parcel maps from the Department of Records, real estate transactions from the Bureau of Revision of Taxes, surveys of vacant properties from Office of Licenses and Inspections, demographic data from the U.S. Census Bureau, and PHS’ own data on cleaning and greening events. From the data, Azavea teased out key metrics: locations of vacant parcels over time, locations of real estate transactions over time, and locations of cleaned and greened parcels over time. Azavea then used exploratory spatial data analysis techniques to identify and visualize temporal and spatial patterns in the data and help answer PHS’ research questions. While the results of the statistical analysis were inconclusive—mostly because sales of vacant lots are rare events—the overall study did reveal key neighborhoods with both high numbers of cleaned and greened lots and relatively high numbers of sales of vacant lots from 2000 to 2008.
Outcomes: Azavea delivered a series of charts and maps for PHS staff to use in presentations to stakeholders and as the basis for future grant-seeking efforts. Both PHS and Azavea are committed to further exploration of the relationship between greening efforts and neighborhood redevelopment.
Website: http://www.pennsylvaniahorticulturalsociety.org
Keywords: mapping, database development, spatial analysis, exploratory spatial data analysis, ESDA, data visualization, data mining, spatial patterns, temporal patterns, vacant land, Philadelphia, land stabilization, parcel data