The service breakdown of the 390,000 participants of the Thrift Savings Plan at the end of 2003 were Army: 15 percent; Marine Corps: 20.2 percent; Navy: 32.2 percent; Air Force: 21.2 percent; Public Health Service: 56.4 percent; and National Oceanic and Atmospheric Administration 68.0 percent. Although significant, Army Lt. Col. Janet Fenton of Armed Forces Tax Council thinks too many are missing out on this tax-deferred savings vehicle. Citing the case of a Marine sergeant who invested his $30,000 re-enlistment bonus in the TSP, she says that, assuming a 7 percent rate of return, the $30,000 is projected to be $345,000 by the time he reaches age 60. And if he continues to contribute to TSP throughout his career, he could rack up more than $1 million saved by the time he retires. In addition, TSP is portable when he leaves active duty.