3.3 Response rates

The overall response rates for the 2021 Census are higher than for the 2016 Census, but lower than those of the 2011 Census. They are similar to response rates achieved in other censuses in Canada and the United Kingdom (both conducted during the pandemic in 2021), and higher than the response rate in New Zealand, when their Census was conducted in 2018 (pre-pandemic). This was an excellent outcome for Australia given the challenges of conducting a Census during a pandemic.

In the 2016 Census, too many non-responding dwellings were deemed as occupied on the Census night that were unoccupied. This was due to dwellings being deemed occupied where there wasn’t sufficient information in the field to determine occupancy. This resulted in some dampening of estimated response rates. Improvements in response rates in 2021 are largely due to an increase in the number of responding dwellings as a proportion of all dwellings which may in part be due to the pandemic causing more people to be counted at home. Improvements are also related to improved occupancy determination. Irrespective, it is an important quality improvement in the 2021 Census.

Person response rates can be viewed in two ways:

• where people were on Census night (their state of enumeration); and
• where people usually live (their state of usual residence).

In reviewing both indicators across each state and territory, the response rates achieved in 2021 were higher than those of 2016. They were also generally lower than those of 2011 with the exception of the Australian Capital Territory and Western Australia for place of enumeration, but they are comparable.

The person response rate (state of enumeration) for the 2021 Census was 95.8%, up from 94.8% in 2016 but lower than the rate in 2011 of 96.3% (see Figure 3.3.1). The highest person response rates were observed in the Australian Capital Territory (97%) and in South Australia (96.9%), while the lowest was for the Northern Territory (91.3%).

Across most of the states and territories, the response rates for occupied private dwellings reflected the pattern for Australia, namely higher in 2021 than in 2016 and lower than in 2011 (see Figure 3.3.3). Some of this is due to a higher level of response in 2021 and some may be due to the occupancy determination issue that was more prominent in 2016. However, Western Australia, the Northern Territory and the Australian Capital Territory are exceptions to this finding, with the rate achieved in 2021 higher than those achieved in both 2011 and 2016. Nevertheless, the rate for the Northern Territory continues to be lower than the other states and territories at 92.8% in 2021 and this reflects the difficulty in enumerating this part of Australia due to its remote nature, diversity of language groups, more transient population and a tighter labour market.

Approximately three per cent (2.9%) of the persons in the 2021 Census population counts were counted in non-private dwellings, down from about four per cent in 2016. The reduction reflects the impact of COVID-19 restrictions on movement in certain jurisdictions. Overall response rates were similar to 2016 (see Table 3.3.1). However, response rates in staff and nurses’ quarters show a marked decline, pointing to difficulty in enumerating settings including staff quarters in remote mining camps. The response rate for people in hospitals was also lower. This result is likely due to the difficulties in enumeration of hospitals during COVID-19 lockdowns.

As is the case in other countries, the 2021 Census relied on and strongly encouraged a digital first approach, while at the same time providing the option of a paper form for those unable or unwilling to complete online. Uptake of the online option by respondents has increased significantly over the past three censuses and has resulted in an associated increase in data quality, as online response is aided by: better sequencing through the form (skipping over questions that are irrelevant based on prior responses); the use of error messages to better guide respondents; and targeted supplementary questions to obtain more detailed responses from respondents.

The Australian Capital Territory had the highest online response of all the states and territories (93.2%), followed by Western Australia (82.4%) (see Table 3.3.3). Tasmania and South Australia had the lowest online response (61.3% and 71% respectively). The Northern Territory had the largest increase in the rate of online take up from 49.4% in 2016 to 74.9% in 2021. It should be noted that online uptake across areas is impacted by the mode of delivery and those states in which more paper forms were delivered had a lower online uptake.

As with overall non-response, total item non-response rates have declined since 2016 and are similar to 2011.

The main contributor to total item non-response is people who do not respond to the Census at all. While key variables (Age, Sex, Marital status and Usual residence) for a non-responding person are imputed (a process that attempts to fill in basic information for the people who didn’t respond to the Census), the remainder of the questions (data items) are set to either ‘not stated’ (and treated as ‘item non-response’) or not applicable, dependent on the imputed age of the person.

Figures 3.3.4 and 3.3.5 show item non-response rates for 2011-2021. The larger blue and orange bars represent the non-response rates which include imputed people (that is people who are not on a Census form). The shorter bars in the same graph show non-response rates for people who responded to the Census but did not answer a particular question. For those people who responded to the Census in 2021, item non-response is lower than in previous censuses for almost all items. Overall, the 2021 Census was more successful than previous censuses in getting people to complete more items as shown in Figure 3.3.4 and 3.3.5. Figure 3.3.6 shows item non-response for a range of dwelling variables.

Analysis of changes in person response rates at the Statistical Area Level 4 (SA4) level between 2016 and 2021 in Table 3.3.4 show that, in 39.8% of the SA4s, the improvement has been more than one percentage point (SA4s are the largest sub-state regions in the Australian Statistical Geography Standard). Most of the inner-city areas across the nation fall into this category. For a further 46.6% of SA4s, there has been an improvement of less than one percentage point. In 13.6% of cases, there was a decline in response. This group is dominated by the more remote areas. This is where field staff recruitment difficulties were most prevalent.

There have been increases in the person and dwelling response rates since 2016, nationally and for all states and territories. This is due to an increase in responding dwellings as a proportion of all dwellings and may also in part be due to improved occupancy determination. However, it should be noted that in some areas (mostly in remote areas), response rates have declined, and quality may be affected in these areas. Households completed the 2021 Census online at a much higher rate than previously, with about 79% of responding dwellings doing so and this will have had a positive impact on data quality. Item non-response rates were generally lower than in 2016, partly due to the lower number of imputed persons in 2021, and partly due to the high online form uptake. These will also lead to an improvement in data quality.