BALTIMORE — Police chiefs, criminologists and federal officials are calling for better and more accurate data on crime as the nation grapples with gun violence but fails to keep a simple tally of the total number of people shot across the country each year.

The FBI takes a census on crime each year with data from local police departments, but many don’t specifically track when people are shot and survive. Those nonfatal shootings are often recorded under a broader category of aggravated assault, which also includes stabbings, serious beatings and other crimes.

Without that information, police and policymakers say, they can’t gauge the full extent of gun violence in America. Homicides are tracked in a distinct category.

“The fact that we don’t count the number of people who are shot is just astonishing because that’s a better barometer of that kind of violence than just homicides,” said Chuck Wexler, the executive director of the Police Executive Research Forum, which helps police departments craft policy and strategies.

Violent crime trends came up during the recent presidential race, when President-elect Donald Trump called attention to a spike in homicides in recent years in a number of U.S. cities – even as President Obama noted a long-term decline in the nation’s homicide rate.

The debate focused attention on violent crime in America at a time when policing has come under heightened scrutiny after numerous killings of unarmed black men by police.

The lack of more detailed data was flagged recently by the U.S. Department of Justice in an annual report on the state of policing in the United States. The report noted that police chiefs, during recent summits on escalating urban violence, recognized that their crime analysis was limited by the fact that not all shootings, such as those that don’t result in a homicide, are tracked.

More accurate and immediate data on fatal and nonfatal shootings “could be vital in combating violent crime and in building community trust,” said the report from the department’s Office of Community Oriented Policing Services.

Wexler said it’s difficult to discern whether an aggravated assault with a deadly weapon means someone was pistol-whipped or shot.

“There are all different kinds of categories, and it’s incredibly important to map hot spots, if you will, or patterns to know if people were shot at or shot or threatened in some way,” he said. “Each of those categories are important.”

Some cities are grappling with targeted violence, while others are struggling with gang warfare in which bullets are shot into crowds indiscriminately, said Daniel Webster, director of the Center for Gun Policy and Research at the Johns Hopkins Bloomberg School of Public Health. Each scenario requires different policing strategies, he said, and making those decisions requires accurate data.

“We first need to define our problems accurately,” Webster said.

Police chiefs, including Baltimore Police Commissioner Kevin Davis, believe a requirement to specifically track shootings should have been implemented nationwide years ago.

Baltimore began recording nonfatal shootings as a separate crime category in 2000. Davis, in a recent speech to business leaders at the Greater Baltimore Committee, referred to nonfatal shootings as “unfinished business,” stressing that in Baltimore, these crimes are often the start or part of a string of shootings that can end with homicides.

Milwaukee Police Chief Edward A. Flynn, whose department also collects statistics on nonfatal shootings, said that relying on a broad category of aggravated assault data is an ineffective way to spot and address trends in gun violence.

“If we can reliably extract nonfatal shooting data across jurisdictions,” he said, “we will have a much more useful comparative metric.”

The Baltimore Sun, in a yearlong investigation, compiled crime statistics on gun violence from the nation’s largest cities, including nonfatal shootings, necessary to calculate the lethality of gun violence over the past five years. Half of the 30 biggest cities kept the necessary data.

The Sun’s investigation found that 1 out of 3 people who were shot died of their wounds in Baltimore, Washington and New Orleans – a distinction that ranked them as the most lethal. The Sun also found that the odds for gunshot victims worsened in at least 10 of the nation’s largest cities last year.

Several factors were behind those trends. In Baltimore, the number of victims shot in the head or multiple times has increased dramatically over the years. And in a number of places, gun-seizure data shows criminals are wielding higher-caliber guns and more large-capacity magazines.

The information collected by the FBI from local police departments across the country is compiled in the Uniform Crime Report. The report, which hasn’t changed significantly since it was started in 1930, is one of two crime surveys the agency conducts. Both provide incomplete information, the DOJ report said.

“The two currently available crime databases run by the federal government cannot provide high-quality and promptly available data about the incidence of crime,” the report said.

The second crime database run by the FBI, the National Incident Based Reporting System, is a program created in 1988 to record more specific national crime data than the Uniform Crime Report. But only about one-third of all U.S. law enforcement agencies use the new system, the DOJ report noted, and it doesn’t require agencies to report nonfatal shootings as a separate category.

Both the Department of Justice and the Centers for Disease Control and Prevention provide annual estimates of nonfatal shootings, but the information is based on limited surveys.

“More accurate and complete data would definitely help efforts to prevent firearm violence,” said Garen J. Wintemute, an emergency department attending physician and the director of the Violence Prevention Research Program at the University of California-Davis Health System in California. “Our current estimates of nonfatal shootings are based on a small sample of emergency departments.”

Stephen G. Fischer Jr., FBI chief of multimedia productions, said changes to the Uniform Crime Report system could require Congress to act. The agency also has a special policy advisory board to review issues raised by law enforcement partners and other agencies. The board can then make recommendations to the FBI director.

On a local level, many police departments don’t keep detailed shooting data because they haven’t modernized the way they track crime. Criminologists say police need to address those shortfalls, not just to record more detailed statistical information, but to use the data to inform policing strategies.

“Some police departments, particularly those in large cities, are becoming increasingly sophisticated about using crime and other data,” said Thomas Abt, senior research fellow of criminal justice policy and management at the Harvard Kennedy School. “Unfortunately, many others are years or even generations behind, using only the most rudimentary information systems, conducting almost all their business on paper, making it next to impossible to track or analyze.”