Figures released by the Transactional Records Access Clearinghouse at Syracuse University on Sunday indicate that 6,472 individuals have been referred to prosecutors on charges related to terrorism by the FBI and other authorities.
Yet only a small number of these ever had their day in court with 64% of cases deemed not worth prosecuting and another nine percent either dismissed by judges or found not guilty.
Of the 27% found guilty only 14 individuals received prison sentences of 20 years or longer, with 67 receiving between five and 20 years.
Overall, of the 1,329 individuals who were sentenced, 704 received no prison time at all, and an additional 327 received sentences ranging from one day to less than a year.
The authors of the report said the figures had raised questions about "the basic competence of the Bush administration in managing the overall response of the United States to terrorism."
Questions about whether US arrests on terrorism charges are driven by political motives arose last June when seven residents of Miami were detained on accusations of plotting acts of terrorism, including a possible bombing of the Sears Tower in Chicago.
However, officials later acknowledged that the suspects mostly talked about the attack and their plot was "more aspirational than operational."