The next release of detailed data about U.S. residents from the 2020 census will be postponed until next year because the U.S. Census Bureau said Wednesday that it needs more time to crunch the numbers, including implementing a controversial method used to protect participants' identities.

The delays leave government budget-makers, city planners and researchers in a lurch because the detailed data are used for planning future growth, locating schools or firehouses and research.

“The truth of the matter is we need this data,” said Eric Guthrie, a senior demographer in the Minnesota State Demographic Center. “The longer we delay, the less use they are when they are finally released because they aren’t as fresh.”

Two sets of detailed data about U.S. residents' age, sex, race, Hispanic origin, relationships in households and housing won't be released until May 2023. The statistical agency previously had planned to release the data sets later this year.

A subsequent round of detailed data on race and ethnic groups won't be released until August 2023. Other rounds of data on household relationships will be made public later in 2023, according to the Census Bureau.

The delays mean the detailed data from the once-a-decade head count of every U.S. resident will be three years old when they are released next year.

Last year, the Census Bureau released state population counts used to determine how many congressional seats each state gets, as well as redistricting data used for drawing congressional and legislative districts. But both data sets from the 2020 census don't provide detailed information about households, ages or families.

For instance, when it came to age, the redistricting data only had numbers about the population grouped into 18 years and older or younger than 18, without age breakdowns provided in the detailed data.

The privacy method is being used for the first time by the bureau in the 2020 census. Differential privacy adds intentional errors to data to obscure the identity of any given participant. It is most noticeable at the smallest geographies, such as census blocks.

Bureau officials say it’s necessary to protect privacy in a time of increasingly sophisticated data mining, as technological innovations magnify the threat of people being “re-identified” through the use of powerful computers to match census information with other public databases.

The Census Bureau released sample data last month that included the application of the method to the detailed data, and it's still gathering feedback from people who use the data.

“These data are so important that we need to give the Census Bureau time to make them right,” Guthrie said. “They are building the plane while they are flying it. They haven’t done this before. Nobody has done this before.”