The FY2000 National Defense Authorization Act provided authority to members of the armed services to participate in the federal thrift savings plan (TSP), whose structure is similar to the Civil Service Retirement System. A cost analysis by the Federal Thrift Retirement Investment Board found that extending the TSP to reservists is a poor idea because of the excessive cost of administering many small accounts. However, the authors conclude that although reserve TSP accounts are likely to be numerous and small on average, (a) a relatively small number of reservists are likely to participate and (b) reserve accounts will be large of prior service personnel can transfer their active-duty balances.