Federal agencies have a long history of releasing data to the public, and they also have a legal obligation to protect the confidentiality of the individuals and organizations from which the data were collected. Federal agencies have successfully balanced these two objectives for decades. With the new emphasis on expanding public access to federal data, coupled with the increasing availability of data from other sources, federal agencies are continuing to ensure that the combination of data already available and the data they are preparing to release does not enable the identification of individuals or other entities through what has been termed the "mosaic effect." The concept of a mosaic effect is derived from the mosaic theory of intelligence gathering, in which disparate pieces of information become significant when combined with other types of information.
To gain more insight into the mosaic effect and its implications for the continued release of data to the public while minimizing the risk of disclosing personal information, the Office of the Assistant Secretary for Planning and Evaluation (ASPE) in the U.S. Department of Health and Human Services (HHS) contracted with Mathematica Policy Research to convene a technical expert panel (TEP), prepare background materials, and summarize what was learned from the panel discussion and the background research in a final report.