techniques for masked data sharing,
procedures for reducing reidentification risks (including safer data and safer settings), and
techniques to reduce the sensitivity of the data being linked.
Techniques for masked sharing or linkage include list inflation, third-party models, and grouped linkage. Secure transfer is aided by techniques, such as encryption, as well as physically secure transfer vehicles (e.g., secure data lines). Safeguard reviews can help ensure that security measures are being followed in another agency. Obtaining consent or providing the ability to “opt out” may be necessary for at least some linkage projects. One approach, used in the Health and Retirement Study, is an explicit consent form, which asks the respondent’s permission for specific records to be transferred from SSA to the University of Michigan for the purpose of linkage. The basic physical and electronic security approaches that are used to protect any data stored electronically also are relevant for information resulting from record linkage. These include access controls, audit trails, and storage strategies. (NRC, 1997; IRS, 2000; Jabine, 1993; GAO, 2001b; 2000a,b,c; 1999; 1998). Stewardship involves compliance with relevant laws as well as the coordination of project-by-project decisions, (which may include whether or not to conduct a specific linkage or whether to release linked data); systems for accountability; and organizational culture.