(RNS) The threat of homegrown Islamic terrorism is "tiny" and often exaggerated by government officials, a leading anti-terrorism expert said in a report released Wednesday (Feb. 8).

Charles Kurzman, a sociologist at the University of North Carolina at Chapel Hill and a researcher at the Triangle Center on Terrorism and Homeland Security, said 20 Muslim Americans were indicted for violent terrorist plots last year, down from 26 in 2010.

Kurzman's report, "Muslim-American Terrorism in the Decade Since 9/11," said that compared to the 14,000 murders in the U.S. last year, the potential for Muslim Americans to take up terrorism is "tiny."

In the 10 years since the 9/11 terrorist attacks, 193 Muslim Americans have been indicted in terrorist plots, or fewer than 20 per year, Kurzman said.

Just one of those indicted last year was actually charged with carrying out an attack -- Yonathan Melaku, who fired shots at military buildings in northern Virginia -- compared to six Muslim Americans who carried out attacks in 2010, including Faizal Shahzad, the failed Times Square bomber.

"This number is not negligible -- small numbers of Muslim Americans continue to radicalize each year and plot violence," Kurzman wrote. "However, the rate of radicalization is far less than many feared in the aftermath of 9/11."

The report was based on research Kurzman conducted for his 2011 book, "The Missing Martyrs: Why There Are So Few Muslim Terrorists."

Since 9/11, Muslims have turned in terrorism suspects in 52 of 140 cases in which the source of the tip could be identified. The report also found that terrorists do not fit any single ethnic profile. In 2011, 30 percent of terror suspects were Arab; 25 percent were white; and 15 percent were African-American.

Other important report findings: Two suspects in 2011 received terrorist training abroad, down from eight in 2010 and 28 in 2009. In addition, about a third (35 percent) of terror suspects since 9/11 has been converts to Islam. 

The number of Muslim Americans arrested for funding or supporting terrorists is also declining, Kurzman said. Compared to 2010, when 27 Muslim Americans were arrested for supporting terrorism, only eight were arrested last year. 

The report makes clear that since a spike in 2009, when 49 Muslim Americans were charged with terrorist plots or attacks, an expected wave of terrorism that prompted frequent terror alerts simply has not materialized.

While terrorism alerts are an understandable precaution, Kurzman said, they also create "a sense of heightened tension that is out of proportion to the actual number of terrorist attacks in the United States since 9/11."

The Department of Justice, which has jurisdiction over prosecuting terrorist plots, did not return a call for comment.