The next time you're surveyed by the Bureau of Statistics it'll know more about you than you think you've told it.

The bureau says it'll be able to "enhance" its future surveys by using answers from the census that it believes are from the same person. So if you tell next Tuesday's census your place of birth or religion or family circumstances the answers might be added to the answers you give to future surveys using a "statistical linkage key" that will be created from the name you submit with the census.

For the first time, your name will be held for four years, instead of being destroyed after processing as has happened in the past. However, the linkage keys will be kept indefinitely, meaning the answers to future survey questions can be linked to answers from the census even after the names have been removed.

"There are likely to be some scenarios when it provides a benefit to the people we are surveying," explains the head of the Bureau's census program, Duncan Young. "We won't have to ask for as much information."