Gentrification Analysis

The rent gap is the difference between the ground rent a site currently earns under its existing, often disinvested use and the potential rent it could earn under its 'highest and best' redeveloped use. Neil Smith argued in 1979 that gentrification happens when this gap grows wide enough that reinvesting capital — renovating or redeveloping — becomes profitable. It matters because it locates the driver of gentrification in capital flows and land economics rather than purely in the tastes of incoming residents, which reshapes how analysts and policymakers interpret and respond to neighbourhood change.

The key distinction is displacement. Ordinary improvement raises a neighbourhood's status while incumbent residents stay and benefit; gentrification involves the replacement of lower-income, often long-tenured residents by higher-status newcomers, frequently under economic pressure. Good analyses therefore pair upgrading indices (rising income, education, rents) with displacement indicators such as falling shares of low-income renters, rising rent burden, eviction filings, and out-migration of incumbents, rather than reading rising prices alone as proof of gentrification.

Census tracts (or block groups) are the finest geography for which consistent, repeated socioeconomic data — income, education, tenure, rent, value — are publicly available over time, making them the practical building block for measuring neighbourhood change. The trade-off is that tracts are imperfect proxies for lived neighbourhoods, their boundaries can shift between censuses, and aggregation within them can hide internal heterogeneity, so results must be read with the modifiable areal unit problem in mind.