What is a census?

What is it?

A census an official count or survey of everyone in a population. Censuses help us to get an accurate picture of the population and dwellings so we can make better decisions about how to share resources and provide support.

In New Zealand, Stats NZ are required to run a census every 5 years by the Statistics Act of 1975. Every individual and household in New Zealand on the night of the census are legally required to take part, including people visiting New Zealand.

Why do we have a census?

You might wonder why the census is legally required? It turns out that we need data about our country in order to make better decisions about our future. The data from the census is used in many, many places in the government, including:

• Deciding electorate boundaries.
• Deciding how many Māori seats we have in parliament.
• Deciding what the government spends on things like health funding, transport, education, housing, social welfare, and much more.
• Understanding how New Zealanders are doing so political parties can make better funding decisions.
• Projecting what might happen in the future like population growth.

People outside of the government use census data too. For example, many iwi use census data to understand where people in their iwi live and the kinds of work that they do.

What data does it have?

The Census questions change a little each time, but typically the census has a range of demographic data like age, ethnicity, iwi, gender, family size, education level, job title, employer industry, income, house size, and more. Sometimes Stats NZ adds questions to the census about other important topics like health and disability.

Stats NZ are responsible for making sure they ask the right questions to enable the government to deliver services. This is why some people have been asking for the census to include questions on sexuality, and to make gender questions more inclusive.

There are two different types of questions in the census — household and individual — to help Stats NZ get a better picture of what is happening in NZ.

How does a census work?

Once Stats NZ have decided on the questions, they test them with lots of people to make sure they work. Once the questions are ready, Stats NZ needs to get them to us to answer. The 2018 census was the first census to be digital-first meaning that Stats NZ sent everyone a code to complete the census online. Before then, Stats NZ delivered every household in NZ received a set of census forms, including a household form and an individual form for every person in the household. Unfortunately, the 2018 census didn’t go smoothly, and had lower response rates than usual, especially for some parts of New Zealand, and some groups of people like Māori.

Once a census form is completed, the data is stored by Stats NZ. Some data, especially data from paper forms where free-form answers can be written, needs to be coded by Stats NZ. This means they need to look at what was written and match it to one of the statistical standards they use like ANZSCO (the standard for occupation classifications) or ANZSIC (the standard for industries).

Statisticians then work to aggregate (group) the data to get statistics for different areas like all of NZ, by region, by territorial authority, and more.

Data privacy

The data from the census is very detailed, and is released at different levels of aggregation, such as by region or council area (territorial authority). Some data is also released about much smaller areas of 30-60 dwellings/60-120 people.

Because the data is so detailed, Stats NZ have to take extra care to protect privacy. This means that some data isn’t released at very detailed levels because it would be too easy to identify somebody. Stats NZ also randomly round numbers up or down to multiples of 3 to protect privacy.

Original copies of census forms are kept by Stats NZ and stored as part of the Integrated Data Infrastructure (IDI) where they are linked with other data collected about you by government agencies.

Researchers can access the IDI, but they can’t see your name or other identifying details. Researchers use IDI access to answer complex questions like understanding the impact of the Christchurch Earthquake on children.