One in five screeners left between Oct. 1, 2006, and Sept. 30, 2007, federal Office of Personnel Management figures show. The turnover rate was identical the year before. Attrition for the rest of the federal government was 8% in 2006-07.

"Twenty percent (turnover) is pretty high," former Homeland Security Department inspector general Clark Ervin says. "You want people who are as sharp and experienced as possible, and that's why it's a concern."