Ted is writing things
Every 10 years, the US Census Bureau asks every American household a series of questions. How many people are living here? How old are they? What is their race and ethnicity? What is their relationship to each other?
The collected answers have very high quality, for two reasons. First, all households have to respond truthfully to these questions, by law. Second, the US Census Bureau has a legal duty to keep the answers secret for 72 years after each survey. Both aspects are key to convince everyone to answer truthfully. Appealing to people's sense of civic duty also helps!
What is the data used for, then? The Census Bureau aggregates it and publishes statistics about the US population. A lot of statistics: in 2010, it released over 150 billion statistics about the US population. These statistics then have many applications: scientific research, informing public policy, determining election districts, etc.
Confidentiality is central to the Census Bureau's mission. By law, they have to make sure that nobody can use their data to find out information about individuals. Disclosing such information even comes with criminal penalties! This has led to the creation of an entire field of study: statistical disclosure control. It predates even the oldest definition of privacy mentioned on this blog (k-anonymity).
