Charles Kurzman, the author of the report for the Triangle Center on Terrorism and Homeland Security, called terrorism by Muslim Americans “a minuscule threat to public safety.” Of about 14,000 murders in the United States last year, not a single one resulted from Islamic extremism, said Mr. Kurzman, a professor of sociology at the University of North Carolina.

The report also found that no single ethnic group predominated among Muslims charged in terrorism cases last year — six were of Arab ancestry, five were white, three were African-American and two were Iranian, Mr. Kurzman said. That pattern of ethnic diversity has held for those arrested since Sept. 11, 2001, he said.

Forty percent of those charged in 2011 were converts to Islam, Mr. Kurzman found, slightly higher than the 35 percent of those charged since the 2001 attacks. His new report is based on the continuation of research he conducted for a book he published last year, “The Missing Martyrs: Why There Are So Few Muslim Terrorists.”