The collection of census data is important for planning Australia's future and to prioritise government spending, and is particularly pertinent to the housing sector. 

"The data collected has been extraordinarily useful in working out demographic trends that affect the housing market," says Louis Christopher of SQM Research.

But millions of Australians last night were prevented from completing the survey, which was presented online for the first time, when the system would not load, and data could not be saved.

The Australian Bureau of Statistics late last night released a statement saying the Census system was down, and revealed this morning the system had been infiltrated by foreign hackers.

"It was an attack, and we believe from overseas... It was quite clear it was malicious," the Australian Bureau of Statistic's chief statistician David Kalisch told ABC radio on Wednesday.

Michael Matusik of Matusik Property Insights lists seven trends he expects to emerge from the census data that have huge implications for the housing sector - assuming the data will be collected successfully.

1. An increase in household size, including greater numbers of children, and multigenerational and shared households.

2. An increase in single and double-occupant households.

3. The casualisation of the workforce.

4. A fall in real wages since the last census.

5. Fewer house moves, and greater length of tenancies.

6. Extra space is made use of, for example by renting out a room on Airbnb.

7. Lower rates of home ownership.

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