Table 1.

Table 1 Some Examples of Re-identification Attempts in General Data Sets and of Health Data Sets ^∗

General Examples of Re-identification
AOL search data 29–31	AOL put anonymized Internet search data (including health-related searches) on its web site. New York Times reporters were able to re-identify an individual from her search records within a few days.
Chicago homicide database 32	Students were able to re-identify a significant percentage of individuals in the Chicago homicide database by linking with the social security death index.
Netflix movie recommendations 33	Individuals in an anonymized publicly available database of customer movie recommendations from Netflix are re-identified by linking their ratings with ratings in a publicly available Internet movie rating web site.
Health-specific Examples of Re-identification
Re-identification of the medical record of the governor of Massachusetts 34	Data from the Group Insurance Commission, which purchases health insurance for state employees, was matched against the voter list for Cambridge, re-identifying the governor's record.
Southern Illinoisan vs. The Department of Public Health 35, 36	An expert witness was able to re-identify with certainty 18 out of 20 individuals in a neuroblastoma data set from the Illinois cancer registry, and was able to suggest one of two alternative names for the remaining two individuals.
Canadian Adverse Event Database 37	A national broadcaster aired a report on the death of a 26 year-old student taking a particular drug who was re-identified from the adverse drug reaction database released by Health Canada.

^∗ The former type of data can contain health information (as in the case of the individual re-identified in the AOL example), and life style and sexual orientation information (as in the case of one of the individuals re-identified in the Netflix example).