When the 1940 census was collected, the public was reassured that the information it gathered would be kept private. “No one has access to your census record except you,” the public was told. President Franklin Roosevelt said: “There need be no fear that any disclosure will be made regarding any individual or his affairs.”

Apparently the limits of what the government can do with census information have their limits. Today the 1940 census goes online.

When the Census Bureau transferred the data to the National Archives, it agreed to release of the data 72 years after its collection. So much for those privacy promises.

Adam Marcus of Tech Freedom writes on C|Net:

Eighty-seven percent of Americans can find a direct family link to one or more of the 132+ million people listed on those rolls. The 1940 census included 65 questions, with an additional 16 questions asked of a random 5 percent sample of people. You can find out what your father did, how much he made, or if he was on the dole. You may be able to find out if your mother had an illegitimate child before she married your father.

To be sure, this data will open a fascinating trove for researchers into life 70 years ago. But the Federal Trade Commission would not recognize a “fascinating trove” exception if a private company were to release data it had collected under promises of confidentiality.

Government officials endlessly point the finger at the private sector for being a privacy scourge. Senator Al Franken did last week in a speech to the American Bar Association last week (text; Fisking). He’s the chairman of a Senate subcommittee dedicated to examining the defects in private sector information practices. Meanwhile, the federal government is building a massive data and analysis center to warehouse information hoovered from our private communications, and the Obama Administration recently extended to five years the amount of time it can retain private information about Americans under no suspicion of ties to terrorism.

Marcus has the bare minimum lesson to take from this episode: “Remember this in 2020.”