Anti-Semitic incidents were down in this country in 2018, but the attacks became more violent. And of those committed by extremists, all of the perpetrators were identified as white supremacists.

These are some of the data points in the Anti-Defamation League’s Audit of Anti-Semitic Incidents for 2018, released today. The annual report counted 1,879 anti-Semitic acts — including assault, vandalism and harassment — and 3,044 total incidents of hate, extremism, anti-Semitism and terror in the United States last year.

Of the anti-Semitic incidents, according to the report, 249 acts (13 percent of the total) were traced to known extremist groups or individuals inspired by extremist ideology. Oren Segal, director of the ADL Center on Extremism, told J. in a press call that all were committed by white supremacists.

“White supremacy is a global terror threat,” said ADL CEO Jonathan Greenblatt. Even so, he cautioned, “Neither side of the political spectrum is exempt from intolerance. The idea that this is a problem with only one side is wrong.”

Most troubling, he said, is the increase in violence, despite a 5 percent drop in overall numbers from 2017.

Anti-Semitic assaults — physical attacks on individuals because they are Jewish — doubled in 2018, with 39 separate attacks reported to the ADL. Some included multiple victims, most notably the October shooting at the Tree of Life synagogue in Pittsburgh, where 11 were killed.

Greenblatt attributes the increased violence to a “normalization of anti-Semitism” that he said has occurred “in recent years.”

Though the ADL’s audit does not include online expressions of anti-Semitism, Greenblatt said online and real-world hate are entwined. “Social media allows the poison to spread, and individuals are able to find content and become radicalized,” he said. “It’s a combustible mixture.”

Segal explained: “Extremist groups use social media to crowdsource. They put up flyers available for anyone to download. That’s why you see similar wording in flyers” found in different cities. Last year, anti-Semitic flyers were left at more than 200 Jewish institutions by white nationalists, he said.

“They physically approached these institutions to leave their flyers. That shows the role of extremist groups in radicalizing individuals.”

Greenblatt, asked how society can “put a lid” on the rising tide of hatred, called it “incumbent on our leaders to lead, long before there is a problem, and reinforce the values of decency, fairness, pluralism and respect for all people.”

The fatal shootings in Poway and Pittsburgh show what can happen, he said, “when we fail to call out the rhetoric of bigotry.”