There are laws to protect the privacy of people who fill out the Census survey.
“By law, personally identifiable information collected for a decennial census is released to the public after 72 years.”- U.S. Census
“Violating the confidentiality of a respondent is a federal crime with serious penalties, including a federal prison sentence of up to five years, a fine of up to $250,000, or both.”-U.S. Census