The Social Insurance Number (SIN) has become an integral part of many transactions in Canada, whether with the federal government for programs like the Canada Pension Plan (CPP) or Employment Insurance (EI), or with provincial governments for programs such as welfare, or with the private sector, which uses SINs for identification. The SIN now underpins some $117.9 billion in government spending, representing nearly one-fifth of all government expenditures in Canada last year. The management and integrity of the SIN system is critical for the proper functioning of the programs in which it provides fundamental identification of participants and, consequently, for the appropriate use of the government resources allocated by these programs.