White supremacists and other far-right extremists have killed far more people since Sept. 11, 2001, than any other category of domestic extremist. The Anti-Defamation League’s Center on Extremism has reported that 71 percent of the extremist-related fatalities in the United States between 2008 and 2017 were committed by members of the far right or white-supremacist movements. Islamic extremists were responsible for just 26 percent. Data compiled by the University of Maryland’s Global Terrorism Database shows that the number of terror-related incidents has more than tripled in the United States since 2013, and the number of those killed has quadrupled. In 2017, there were 65 incidents totaling 95 deaths. In a recent analysis of the data by the news site Quartz, roughly 60 percent of those incidents were driven by racist, anti-Muslim, anti-Semitic, antigovernment or other right-wing ideologies. Left-wing ideologies, like radical environmentalism, were responsible for 11 attacks. Muslim extremists committed just seven attacks.