Census head Duncan Young told Fairfax Media that "over 94 per cent" of occupied households have completed a census form and he expects that to reach 95 per cent by Thursday evening. The census website crashed as an estimated 16 million people tried to log on. "We are certainly past the point that makes it a high quality data set for analysis," he told Fairfax Media. "From here it's about making sure that quality is there for every small population group and every small population area." The collection of online census forms formally closes on Friday, September 23. The final participation rate will be released early next month.

2. How does the participation rate compare? The participation rate in the 2011 census was 96.5 per cent and Mr Young said it was still possible this year's figure could come close to that. Census head Duncan Young. Credit:Sean Davey "Of course we could get up somewhere near where we were last time," he said. "We'll try to get as close to 100 per cent as we can." Young said the 2013 New Zealand census had a 92.9 response rate. The UK targets a 94 per cent participation rate for a "sufficient census" and got a 94.9 per cent rate at its last census.

"By being up over 94 per cent we are comfortably in that range," said Young. 3. How many households? So far more than 8.2 million households have completed a form out of the 8.7 million the bureau estimates were occupied during census night on August 9. There are about 9.8 million dwellings in Australia but Young said over a million of those are unoccupied on any given night of the year. The 2016 census has been marked by debate over privacy but Mr Young said the number of people who have informed the bureau they do not want to fill in a census form is about half of that of 2011.

4. Online versus paper forms About 59 per cent of households have filled in the census online. That's short of the 65 per cent the bureau was targeting but well up on the 33 per cent who completed the census online in 2011. Young said the website outage, which began on census night and lasted nearly two days, contributed to the lower than expected online response rate. Even so, Young said the 2.2 million extra forms submitted online compared with 2011 would improve the quality of this census because online respondents leave fewer questions blank and tend to provide better answers overall. 5. Now for the number crunching

Loading The task of collating and analysing census data is already underway. About 500 bureau staff at a "secure data capture centre" has begun converting answers on forms into statistical data. Young said the higher proportion of forms completed online will allow the census data to be processed more quickly than in the past. The first release of census data will be on April 11, 2017, about two-and-a-half months earlier than in the past. Two further batches of more detailed census data will be released later in 2017.