By Jen Kinney.

As many U.S. cities grow in population, construction cranes and rising luxury condo buildings are dotting skylines. But a recent survey of historic assets in 50 U.S. cities suggests Jane Jacobs was right to believe neighborhoods with a mixture of new and old buildings actually create more of what people want in a city.

Created by the National Trust for Historic Preservation’s Preservation Green Lab, the Atlas of ReUrbanism examines more than 10 million buildings of all ages, scoring urban areas by the median age of buildings, the diversity of ages in an area, and the size of buildings and parcels. According to the report, areas with only new buildings are less likely to promote entrepreneurial activity, density, and diversity than areas with a mixture of new and old.

Places with older, smaller buildings mixed with new development rank high on a score of character, while those with newer, larger buildings of a similar age rank low.

By this measure, the Atlas finds that high character areas also tend to be denser, more diverse, more affordable and provide more opportunity. In other words, they more effectively deliver on the urban promise: a place where anyone can get ahead. Of the 3.2 million small business jobs identified across the 50 cities studied, 59 percent are found in high character score areas, compared to 41 percent in low character areas. Of the 202,767 affordable units, 56 percent were found in high character areas.

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Read the full story at Next City.