Figure 4 above shows that inflation-adjusted single family home prices have increased much faster in subsidy threatened neighborhoods than the average citywide. This suggests that a large number of affordable units are in rapidly-changing neighborhoods where we’d likely want to make preservation a priority.

If this analysis is of interest to you, consider checking out the Furman Center report which uses much more sophisticated data from New York City. For researchers, the next steps in cities like Philadelphia and New York is to study how a dwindling stock of affordable housing particularly in changing neighborhoods may be effecting residents.

Another of PACDC’s major policy objectives is to, “Address and understand the threats and impacts of displacement and expand housing assistance programs’. Data on expired affordable housing and the people who reside there may offer some important insights into the dynamics of neighborhood change and residential displacement.

Imagine if we looked at two comparable families from the same neighborhood – one which was allowed to remain in their unit because the affordable subsidy was preserved, and another whose subsidy expired and couldn’t afford the increase to market rate rents. Was the latter family displaced into a comparatively lower quality neighborhood with say, higher crime rates, inferior schools or fewer fresh food options?

In Philadelphia, this analysis would constitute just one of several policy-induced opportunities to study displacement.

All too often our narrative about neighborhood change is formed by our own observations about changes in the built environment – like the appearance of new cafes or the development of multistory condos.

While these outcomes may be important, what is more relevant is whether these changes have positive or negative impacts on actual people – and it is this people-centric understanding that will help us craft effective comprehensive housing strategies going forward.

Ken Steif is a Doctoral Candidate in the City & Regional Planning Program at the University of Pennsylvania where he studies housing policy and neighborhood change. He also consults professionally and teaches courses in GIS and spatial data science. You can follow him on Twitter @KenSteif.