for what it is worth, philadelphia has a long and sordid history going back to the planning department in the 1960's of intentionally leaving neighborhoods blighted so that they can re-assign, or through urban gentrification, re-define the demographics of a neighborhood.
Philadelphia: Darien Street
Gentrification Amid Urban Decline: Strategies for America's Older Cities, by Michael Lang, reports the process and impact (social, economic, cultural) of gentrification. In particular, we focus on the section of Darien Street (a north-south street running intermittently from South to North Philadelphia) which is essentially an alley in the populous Bella Vista neighborhood. That part of Darien Street was a "back street", because it does not connect to any of the city's main arteries and was unpaved for most of its existence.
In its early days, this area of Darien Street housed only Italian families, however, after the Second World War (1939–1945), when the municipal government spoke of building a cross-town highway, the families moved out. Most of the houses date from 1885 (built for the artisans and craftsmen who worked and lived in the area), but, when the Italian Americans moved out, the community's low-rent houses went to poor African American families. Moreover, by the early 1970s, blighted Darien Street was at its lowest point as a community, because the houses held little property value, many were abandoned, having broken heaters and collapsed roofs, et cetera.[60] Furthermore, the houses were very small — approximately 15 feet (4.6 m) wide and 15 feet (4.6 m) deep, each had three one-room stories (locally known, and still currently advertised as a "Trinity" style house,) and the largest yard was 8 feet (2.4 m) deep. Despite the decay, Darien Street remained charmed with European echoes, each house was architecturally different, contributing to the street's community character; children were safe, there was no car traffic. The closeness of the houses generated a closely knit community located just to the south of Center City, an inexpensive residential neighborhood a short distance from the city-life amenities of Philadelphia; the city government did not hesitate to rehabilitate it.
The gentrification began in 1977; the first house rehabilitated was a corner property that a school teacher re-modeled and occupied. The next years featured (mostly) white middle-class men moving into the abandoned houses; the first displacement of original Darien Street residents occurred in 1979. Two years later, five of seven families had been economically evicted with inflated housing prices; the two remaining families were renters, expecting eventual displacement. In five years, from 1977 to 1982, the gentrification of Darien Street reduced the original population from seven black households and one white household, to two black households and eleven white households. The average rent increased 488 per cent — from $85 to $500 a month; by 1981, a house bought for $5,000 sold for $35,000. Of the five black households displaced, three found better houses within two blocks of their original residence, one family left Pennsylvania, and one family moved into a public housing apartment building five blocks from Darien Street.[61] The benefits of the Darien Street gentrification included increased property tax revenues and better-quality housing. The principal detriment was residential displacement via higher priced housing.[62]