Each year, 311 – New York City's main hub for government information and non-emergency services – receives millions of requests and complaints, including New Yorkers’ gripes about their neighbors. In a new study, ISS researcher Merlin Schaeffer and his colleague Joscha Legewie (Yale University) use 311 complaint data, to track when and where New Yorkers complain about their neighbors making noise, blocking driveways, or drinking in public. They found that these complaints – a defining aspect of urban life – are more likely to occur in areas sandwiched between two homogenous communities, where the boundaries between different ethnic and racial groups aren't clearly defined.

Neighborhood conflict arises from segregation and is particularly prevalent at ‘fuzzy’ boundaries between homogenous neighborhoods. The number of complaints jumped 26 percent from areas without boundaries to those with “fuzzy” boundaries. As the two sociologists explain, ethnic residential segregation strengthens group identities and claims about ethnically defined group turfs. Mixed areas that are sandwiched between two homogenous communities are particularly prone to conflict because these ‘fuzzy’ boundaries are contested, that is, they foster ambiguities about group turf.

To define neighborhood boundaries, the researchers adopted edge-detection algorithms used in science and engineering, including computer vision and image processing. For instance, engineers developing driverless cars rely on these algorithms to detect the boundaries of objects in order to navigate. They applied these edge-detection algorithms to census data on the makeup of New York City’s neighborhoods, which allowed them to identify boundaries between ethnically homogeneous areas and determine how sharp the boundaries are.

Then, using data from 4.7 million time stamped and geocoded 311 service requests from 2010, the researchers tracked complaint calls to measure neighborhood conflict. Indicators of neighborhood conflict include complaints of a blocked driveway, drinking in public, illegal conversion of residential space (such as short-term renting of living space), and certain noise complaints, including loud music or parties.