For the third year in a row, police nationwide shot and killed nearly 1,000 people, a grim annual tally that has persisted despite widespread public scrutiny of officers’ use of fatal force.

Police fatally shot 987 people last year, two dozen more than they killed in 2016, according to an ongoing Washington Post database project that tracks the fatal shootings. Since 2015, The Post has logged the details of 2,945 shooting deaths, culled from local news coverage, public records and social-media reports.

While many of the year-to-year patterns remain consistent, the number of unarmed black males killed in 2017 declined from two years ago. Last year, police killed 19, a figure tracking closely with the 17 killed in 2016. In 2015, police shot and killed 36 unarmed black males.

Experts said they are uncertain why the annual total shows little fluctuation – the number for 2017 is almost identical to the 995 killed by police in 2015.

Some believe the tally may correspond to the number of times police encounter people, an outcome of statistical probability. Other experts are exploring whether the number tracks with overall violence in American society.

“The numbers indicate that this is not a trend, but a robust measure of these shootings,” said Geoff Alpert, a criminologist at the University of South Carolina who studies police use of force. “We now have information on almost 3,000 shootings, and we can start looking to provide the public with a better understanding of fatal officer-involved shootings.”

National scrutiny of shootings by police began after an unarmed black teenager from a suburb of St. Louis was fatally shot by a white police officer in August 2014. The death of 18-year-old Michael Brown sparked widespread protests, prompted a White House commission to call for reforms, galvanized the Black Lives Matter movement and led many police agencies across the nation to examine their use of deadly force.

The attention may have helped police reduce the number of unarmed people shot and killed each year, according to interviews with experts and police departments. Officers fatally shot 94 unarmed people in 2015, but that number has been lower in the past two years, with 51 killed in 2016 and 68 in 2017.

“The national spotlight on this issue has made officers more cautious in unarmed situations,” said Chuck Wexler, the executive director of the Police Executive Research Forum, a Washington-based think tank. Wexler also said that the training that his group developed for dozens of departments to de-escalate police encounters with civilians may be having an impact.

“We are giving officers more options like slowing the situation down and using time and distance to gain a tactical advantage,” he said.

DISPROPORTIONATE NUMBER OF BLACK MALES

While the number of black males – armed and unarmed – who have been killed has fallen, black males continue to be shot at disproportionately high rates, the data shows.

Black males accounted for 22 percent of all people shot and killed in 2017, yet they are 6 percent of the total population. White males accounted for 44 percent of all fatal police shootings, and Hispanic males accounted for 18 percent.

Other patterns also held steady in 2017, according to The Post database.

Police again most frequently used fatal force after encountering people armed with knives or guns, killing 735, a number nearly identical to the 734 armed people and killed in 2015. The number was slightly lower in 2016, with 693 armed with either type of weapon.

White males continued to account for the largest group of people killed while armed with guns or knives, at 330 of those killed. Black males armed with guns or knives were fatally shot in 160 cases last year.

Mental health again played an outsize role in the shootings: 236 people, or nearly 1 in 4 of those shot, were described as experiencing some form of mental distress at the time of the encounter.

In the vast majority of those cases, 88 percent, the deceased people had wielded firearms or other weapons, including a machete, a sledge ax and a pitchfork.

In November, Oklahoma City resident Dustin Pigeon, 29, threatened to set himself ablaze. A police officer shot Pigeon five times after he refused to drop a lighter and lighter fluid, according to prosecutors. In an unusual outcome, prosecutors charged the officer with second-degree murder in the death of Pigeon, saying that Pigeon was unarmed and had posed no threat to the officer.

Mental-health advocates said they have been encouraged by the number of police departments that have created intervention teams to help people in mental distress but were dismayed at the persistence of the number killed.

“We call 911 for other medical emergencies and they bring specially trained medical technicians, but when it’s a mental-health crisis, we send the police,” said Ron Honberg, a senior policy adviser at the National Alliance on Mental Illness, a grass-roots mental health-care advocacy group.

Of all the people shot and killed by police in 2017, one of the youngest was 14-year-old Jason Pero from the Bad River Band of the Lake Superior Chippewa. In November, Jason called 911 to report a man with a knife and then gave a description of himself. Holding a knife, Jason lunged at a sheriff’s deputy, who shot and killed him, according to news reports.

The oldest person killed by police was 91-year-old Frank Wratny of Union Township, Pa., who was fatally shot in March after he confronted police with a gun at his home. Police were responding to a 911 call from a woman who said Wratny had fired at her, according to news reports.

Meanwhile, the number of police officers feloniously killed in the line of duty in 2017 stood at 46, a decline from the 66 recorded in 2016, according to the FBI.

Since the shooting of Brown, some police departments said they have made headway in efforts to reduce the number of people they fatally shoot.

In Los Angeles in 2015, the police department began to emphasize that officers should strive to preserve life in all encounters. Last year, the department began to award a preservation-of-life medal to an officer who makes great efforts to avoid a fatal shooting. The move was derided by local police unions.

Top managers in the department said they think it has made a difference: Last year, Los Angeles Police Department officers fatally shot 15 people, down from 18 in 2016 and 21 in 2015.

First Assistant Chief Michel Moore said the LAPD has provided officers with more training to emphasize de-escalation and has taken steps to hold officers more accountable.

“Our officers are in 1.5 million volatile encounters a year, so shooting someone is an incredibly rare event,” Moore said. “Yet we pull each instance apart and see what factors might have played a role and train our officers to make that rare event even more rare.”

For a third consecutive year, The Post documented more than twice the number of deadly shootings by police that were recorded on average annually by the FBI.

In response to the shooting data compiled by The Post and others, the FBI in 2015 promised to start better information gathering about all police encounters that lead to deaths. This month, the agency said it will launch the new nationwide data collection system.

But the new system will have some of the same limitations that has led the government to annually undercount by half the fatal police shootings. As before, data submissions under the new program will be voluntary.