Three little numbers have made up one of the most important innovations in municipal service delivery in recent years -- 311. Citizens who in the past wouldn’t have known which department or agency to call when there’s a dead animal in their yard or a broken streetlight on their block now can punch in three numbers and easily lodge their complaint.

How effective are cities at responding? Pretty good. Or at least they’re pretty fair about how and where they respond. A series of recent academic studies have found that response times are roughly the same to 311 calls regardless of whether they originate in rich neighborhoods or poor ones.

Brian Hamel and Derek Holliday, a pair of graduate students at UCLA, examined more than 6 million 311 calls from seven major cities around the country, including Chicago, Houston and Los Angeles. They found that a 1 percent increase in neighborhood income led to an average decrease of just 0.16 days in the length of time before a problem was resolved. When they compared how fast cities responded to the same complaints coming from different neighborhoods, there tended to be a faster response in poor neighborhoods for many types of calls. L.A., for instance, is faster to remove graffiti or address homeless encampments in wealthy neighborhoods, but swifter to deal with dead animals and streetlight complaints in less affluent ones. “Overall, we think cities are generally equally responsive to the rich and poor,” Hamel wrote on Twitter.

Their findings jibe with an older Georgetown University study that looked at all the 311 calls made over a decade in Washington, D.C. Over time, as the service became entrenched, an early variation in response times between neighborhoods dwindled down almost to nothing. Calls from predominantly white neighborhoods had actually experienced the slowest response times at first.

There is one catch: A New York University study from 2017 found big differences in who uses 311. Neighborhoods with higher proportions of unmarried, minority and unemployed residents tend to underreport problems. Neighborhoods with higher rents and incomes and residents who are white or Asian call 311 more often, so they end up with more responses, through no intent of the agencies.

Academics who study cities have generally looked at differences between them. It’s encouraging that the type of data tools exemplified by analyzing 311 calls is leading a younger generation of scholars to quantify differences within cities as well. That kind of information can help individual cities learn what they’re doing right and where they fall short.