Rate of census completion much better than expected

More than six million of Australia's nine million households have completed the census, despite problems with the online national survey.

The result is 1.5 million greater than the 4.5 million responses the Australian Bureau of Statistics (ABS) had expected after the online form was taken down for 40 hours due to cyberattacks.

"We actually thought that as few as 50 percent of the Australian population would respond before we needed to start visiting households," ABS census head Duncan Young told Fairfax Media today.

"We are ahead of our original plan, which is quite remarkable when you consider the fact that we did not have our online form available for 40 hours, including for some of our peak period on census night."

The ABS has launched a joint investigation with the nation's defence intelligence agency into the “malicious” cyber-attack, whch blocked most of the population from completing the survey on August 9.

A penalty of $180 per day will be enforced after post-census letters and staff visits cease in mid-September.

With AAP.