Nearly every major U.S. city has seen an increase in murders in 2020 compared with 2019.

Murders have increased over 2019 by at least 50 percent in more than a dozen cities, according to the latest available data from local law enforcement agencies.

In Milwaukee, murders have doubled this year. Baltimore is one of the only cities that saw a decrease in killings.

By late October, the total number of gun homicides in 2020 had already exceeded the year-end total for each of the past four years, according to data tracked by the nonprofit Gun Violence Archive.

The count does not include suicides, which make up the majority of gun deaths.

Meanwhile, other types of crime such as burglary, larceny, and drug offenses declined across the country.

While nearly every type of gun violence spiked this year, mass shootings showed a particularly steep increase. In spite of the social isolation imposed by the pandemic, the number of shootings with four or more victims exceeded any recent year by more than 50 percent.

Children below the age of 18 were shot and killed in greater numbers this year as well.

In New York City, a rash of child shootings pushed the city’s homicide numbers above 400 for the first time since 2012.

The number of fatal accidental shootings also surged. Gun Violence Archive has recorded more than 600 such deaths in 2020.

Nicole Kravitz-Wirtz, an assistant professor who researches violence prevention at the University of California, Davis, said the year’s record gun sales may have played a role. She and her colleagues recently estimated that 55,000 gun owners in California had started keeping a weapon loaded and unlocked in response to the pandemic.