Law-enforcement officers stand at a New York City crime scene.
A crime scene at the New York Port Authority Bus Terminal. Andrew Kelly/Reuters

A new online mapping tool allows you to track long-term trends in violence across dozens of U.S. cities.

On the campaign trail, candidate Donald Trump falsely proclaimed that America’s cities have become increasingly dangerous. “We have an increase in murder within our cities, the biggest in 45 years,” he said. But the reality is that urban violence has declined substantially since its peak during the early 1990s. Then, not more than a year later, Attorney General Jeff Sessions claimed that Trump’s policies were in fact responsible for a decline in urban crime and the end of “American carnage.”

All of which raises the question: Is violence rising or falling? How do we know?

The confusion about trends in crime and violence was the motivation for a new mapping and data visualization tool put together by my colleague Patrick Sharkey at New York University and a team of researchers at NYU’s Marron Institute of Urban Management. Their site, AmericanViolence.org, which was created with support from the Bill and Melinda Gates Foundation, compiles data on murder rates for 80-plus cities over the period 1990 to 2017, spanning the high point of violent crime to the recent decline. The site fills a substantial void by organizing comprehensive, comparable data on murders and murder rates for these cities. Crime data are notoriously unreliable and hard to compare across cities because of differences in how crimes are cataloged and reported. To develop their database, the team supplemented data from the FBI Uniform Crime Reports with data from the Gun Violence Archive and from cities themselves.

a map comparing murder rate in 2016 compared to 1990-1991
A map compares the murder rate per 100,000 people in 77 U.S. cities in 2016 to 1990-1991. (AmericanViolence.org)

The website allows you to look at the broad picture of urban violence across the United States, showing the still-large differences across cities. You can also create charts that enable you to compare long-term trends in urban violence across cities or zoom in to one specific city and see how violence has changed over any time frame. And geeks like me can export and download the data to conduct an analysis. (The first version of the site offers city-level data on murder rates in more than 80 of the largest 100 U.S. cities; the still-to-launch second version will feature neighborhood-level figures on violent crime in 30 to 50 cities.)

Sharkey and company take a deep dive into these data in a detailed report that accompanies the site. They argue that to assess how violence is changing, it is essential to analyze the data over multiple time frames. As Sharkey told me via email: “The most common mistake in interpreting trends in violence is to focus on very short timeframes of a few months or a year, instead of considering the bigger picture of how violence is changing over long periods of time and in different places across the country. We wanted to start by simply describing how urban violence has changed over the short-term and the long-term.”

They start by going back to 1990. The next year, 1991, was a peak for violence urban and otherwise, when nearly 25,000 people were murdered in total across the United States. There has been a remarkable decline since then. The year 2016 saw 18,000 murders in the U.S., 7,000 fewer than in 1991. That said, violence ticked up between 2014 and 2017, but appears to have fallen back since then.

Using the detailed data from their sample of 78 large cities allows them to delve deep inside these broad trends. (Note: the number of cities varies from year to year, depending on the data available for a given time frame). There was a 45-percent decline in murder across these 78 cities, from 12,000 in 1991 to 6,600 in 2017; and an even larger, 57-percent decline in the murder rate over this period. Indeed, the murder rate fell in more than 70 percent of the cities they have data on (56 of 78), in more than 85 percent (29 of 34) cities with 500,000 or more people, and in all 10 cities with populations of 1 million or greater.

In fact, half of this decline in urban violence came from America’s two largest cities, New York and Los Angeles, where there were 1,864 and 744 fewer murders, respectively, in 2017 than 1991. Washington, D.C. saw the largest drop in its murder rate over this period, from 80 murders per 100,000 residents in 1991 to below 17 per 100,000 residents in 2017.

a chart of change in the murder rate for biggest U.S. cities
How the murder rate per 100,000 people has dropped in America’s largest cities. (AmericanViolence.org)
A chart showing the change in murder rate for U.S. mid-sized cities
How the murder rate has dropped in nearly all of America’s cities with populations between 500,000 and 1 million. (AmericanViolence.org)

However, violent crime has had a recent uptick. Nearly three-quarters (60 of 81) of the cities in the database experienced a rise in violent crime between 2014 and 2017, as the overall number of murders across U.S. cities in the database increased by 25 percent. Chicago and Baltimore had particularly large increases in their murder rates over this period, while Newark saw the biggest decrease in its murder rate.

American cities remain the most violent in the advanced world. In 2017, 12 U.S. cities in the database had a murder rate of more than 20 murders per 100,000 people—a threshold used to distinguish the world’s most violent, war-torn places. But this number of cities (12) was down considerably from 32 in the 1990s. And the stark reality is that even with this overall decline, murder and violent crime remain distressingly concentrated at far higher levels in the most disadvantaged and disconnected areas of our cities, as Sharkey’s earlier research has documented.

The good news is the team’s data suggest that the recent uptick in urban violence has leveled off and even reversed in the past year, as the murder rate has again begun to track downward. “The change that has occurred since 2014 is worrisome because it marks a shift from the long-term pattern of declining violence, but the recent increase in violence does not compare in scale or breadth to the fall of violence that has taken pace since 1991,” the researchers write. “The recent rise of violence has barely made a dent in the long-term crime decline.”

As Sharkey sees it, a big problem in the public debates about crime, violence, and guns is lack of accurate data. “More and more data are available to the public,” Sharkey told me. “But the data are scattered across dozens of different websites, and presented in ways that are extremely difficult to understand and interpret. Our goal is to find the best sources of information out there, collect it all and present it in a way that is consistent, easily interpretable, and as accurate as possible.”

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