Why is this such useful information?

Neighborhood businesses depend on foot traffic, and some studies have found that the number of businesses per acre is the most important predictor of whether people are likely to walk in their neighborhoods.

Places with clusters of storefronts are also likely to have stronger residential real estate markets, as walkable urban neighborhoods are at a premium nationally. Metrics like Walk Score have become one of the factors people consider when choosing a neighborhood, and the scores are mostly determined by the volume of amenities within walking distance.

One upshot is that the zoning power gives city government direct influence over the density of residents and storefronts allowed within a given area. Zoning to allow more storefronts doesn’t always guarantee that new businesses will open, but the visualization uncovers where commercial corridors seem to “want” to expand, and where land use could be more supportive of this.

In growing neighborhoods, zoning for greater density or mixed uses can support a greater concentration of storefronts and nearby customers, but this isn’t always universally well-regarded among residents or elected officials.

Council President Darrell Clarke recently indicated an interest in increasing statutory parking minimums in response to increasing residential density in some neighborhoods, and a disagreement over how densely to rezone the Point Breeze Avenue commercial corridor was one of the more substantive differences between Councilman Kenyatta Johnson and Ori Feibush in last year’s 2nd Council District election.

To put Philadelphia in context, out of the 51 largest metros, the city had the fourth highest number (3,084) of storefront businesses within three miles of our central business district in 2014. The median metropolitan area on the list (Pittsburgh, coincidentally) had around 900 storefront businesses within that radius.

As the map shows, though, neighborhood storefront clusters outside of Center City don’t come close to matching the intensity of the central business district, and there’s a question of just how much storefront density a neighborhood corridor needs to be successful.

The report doesn’t offer a specific prescription on this point, but it does show that business districts in some smaller cities can get by with a much lower concentration of storefronts than is typical around center city Philadelphia.

The three-mile area around downtown St. Louis, for instance, has only around 400 storefronts, compared to about 1,700 in Portland. St. Louis also has fewer and smaller minor commercial strips within that radius than Portland does. This is likely a function of higher residential density in Portland.