How important are birthdays? Computer scientist Latanya Sweeney‘s work quantifies the importance of knowing someone’s date of birth when trying to re-identify partially de-identified data. She’s written a series of papers showing how multiple non-name attributes can work together to serve as functional identifiers when matched against publicly available databases like voter lists or public hospital visit data. Per her research, she estimates that:

• 87% of Americans can be uniquely identified by the combination of date of birth, gender, and ZIP code
• 53% of Americans can be uniquely identified by the combination of date of birth, gender, and city
• 18% of Americans can be uniquely identified by the combination of date of birth, gender, and county

However, substituting year of birth for the full day-month-year:

• 0.04% of Americans can be uniquely identified by the combination of birth year, gender, and ZIP code
• 0.04% of Americans can be uniquely identified by the combination of birth year, gender, and city
• 0.00004% of Americans can be uniquely identified by the combination of birth year, gender, and county

Read more:

• Latanya Sweeney’s research on identifiability