Analysis of Household Crowding

Background

Freedom from crowding is one of the six dimensions of housing adequacy recognised by Statistics New Zealand. Crowding in a dwelling occurs where the number of people residing in a household exceeds the capacity of that household to provide adequate shelter and services to its members. Crowding may arise for a number of reasons, including socioeconomic status, cultural preference, social cohesion, limited availability of appropriate housing stock and accepting high occupant density as a means of containing cost.
National and international research has shown that non-European populations, such as Māori and Pacific peoples in New Zealand, live in the most crowded housing (Baker et al 2013). However, this is not just a product of poverty; it is likely that a combination of factors contribute. These include larger household size (including a higher proportion of households involving multiple families or extended families), affordability issues (the household cannot afford a dwelling large enough to accommodate its members), living arrangements and lack of housing stock.
Immigration into New Zealand is also a factor contributing to crowding for some ethnic groups. Factors such as limited large-sized housing stock, cultural living arrangements and low incomes all compound crowding in these groups.

Crowding and health

Best available evidence indicates that housing that is an appropriate size for the householders and is affordable to heat is linked to improved health and may promote improved social relationships within and beyond the household (Thomson et al 2013).
Exposure to household crowding has been found to be related to a number of poorer health outcomes. Crowding is an important risk factor for infectious diseases such as rheumatic fever (Jaine et al 2011), meningococcal disease, respiratory infections (Baker et al 2012) and skin infections (cellulitis) (Baker et al 2013), as well as pneumonia, elevated blood pressure and increased risk of childhood injuries. Furthermore, it has been suggested that adults and children living in crowded households are less likely to access health care services than are those in non-crowded households (Cutts et al 2011).
Looking more broadly into the social sector, there is some suggestion that provision of adequate, affordable warmth may reduce absences from school or work (Thomson et al 2013).

Overview of methods

This study was based on crowding data derived from the 1991, 1996, 2001, 2006 and 2013 censuses. It was analysed at the unit record level by the Ministry of Health in collaboration with Statistics New Zealand.

Glossary

American Crowding Index

This measure of crowding is used once in this report due to the statistical requirements of reporting on the final section ‘Visitors to households’. The American Crowding Index is an alternative measure of household crowding used by the United States Census Bureau. It is defined as the number of usual residents in a dwelling divided by the number of rooms in the dwelling. This measure of crowding is less detailed than the Canadian National Occupancy Standard as it does not take into account the types of rooms in the dwelling nor does it make adjustments for the age and sex of the usual residents.

Canadian National Occupancy Standard (CNOS)

The Canadian National Occupancy Standard (CNOS) is one of several indicators available that is used to evaluate the extent of crowding in New Zealand and was used in previous analyses of crowding using census data. It is the primary measure of crowding used in this report and is used in all sections except the ‘Visitors to households’ section, where statistical requirements meant the American Crowding Index had to be used (see above).
CNOS has been developed by the Canada Mortgage and Housing Corporation to help determine the number of bedrooms a dwelling should have to provide freedom from crowding. The CNOS is based on the number, age, sex and interrelationships of household members.
The CNOS states that:

no more than two people shall share a bedroom

parents or couples may share a bedroom

children under 5 years of age of the same or opposite sex may share a bedroom

children under 18 years of age of the same sex may share a bedroom

a child from 5 to 17 years of age should not share a bedroom with a child under 5 years of age of the opposite sex

single adults 18 years of age and over and any unpaired children require separate bedrooms.

Census 2013

Census New Zealand is the official count of household composition (number of people and their ages and interrelationship status) and the number of rooms in the house. It takes a snapshot of the people in New Zealand and the places where we live.
Data is collected and reported by Area Units, which are aggregations of the meshblocks (the smallest geographic unit for which statistical data is collected by Statistics New Zealand). Area Units are non-administrative, geographic areas that are in between meshblocks and territorial authorities in size. Area units within urban areas normally contain a population of 3000–5000, though this can vary due to such things as industrial areas, port areas, and rural areas within the urban area boundaries.

Confidence interval (CI)

A confidence interval is a range around an estimate that tells us how precise that estimate is; the confidence interval indicates the level of uncertainty in a measurement that occurs due to taking a sample.
The results presented in this report have 95 percent confidence intervals (95% CI). If many samples are selected, the 95% CI encloses the ‘true’ value for the population 95 percent of the time. The sample size of the group influences the size of the confidence interval. Where the sample size is small, the confidence interval is typically wider and the estimate is less precise.

District health boards (DHBs)

District health boards (DHBs) are organisations responsible for providing or purchasing health services in a particular district of New Zealand (although some health services are funded and purchased nationally by the Ministry of Health). There are 20 DHBs in New Zealand, with DHB populations ranging from 30,000 to over 1 million people.
Where possible, census results for crowding data have been broken down by DHB to represent the geographic differences in crowding across New Zealand.

Ethnicity

This report uses total response ethnicity to define ethnic groups. Total response ethnicity includes a person in all the ethnic groups that they identify with. This means that people can appear in more than one ethnic group.

Household crowding

Crowding is shown as a percent and is calculated using the CNOS (a measure of crowding, see above) divided by the total number of people who responded to the occupancy question in the census (as opposed to the total population). Crowding is defined when one or more bedrooms are required in a household.

Jensen Equivalised Annual Household (JEAH) income

Income quintiles have been calculated using the JEAH scale, which compares household income across household types. The scale is constructed so that a two-adult household has a rating of 1; households with fewer members score less than 1 and those with more than two adults score more than 1. The scale also accounts for the fact that children are likely to require less income than adults to maintain a similar standard of living.
JEAH income is calculated for individual households by dividing annual household income by a household’s rating.

Low income

Low income has been calculated using the lowest two quintiles of the Jensen Equivalised Annual Household income (see above); that is, those areas that are in the lowest and second lowest groups for household income.

Rounding

In this report, percentages have been rounded to one decimal place, except for low percentages, which are rounded to two decimal places. Numbers are rounded to the nearest 100 people. Rounding and the exclusion of ‘not stated’ means that numbers and percentages across tables do not always add up to the same total and percentages do not always add up to 100 percent.

Sector of landlord

Sector of landlord refers to the type of organisation or person from whom households rent or lease private occupied dwellings. It can be the private sector (private person, trust or business) or the state sector (Housing New Zealand Corporation, a local authority or city council, or another state-owned corporation or state-owned enterprise, government department or ministry).
A rented private dwelling is a dwelling that is not owned by the usual resident(s) and for which the usual resident(s) make rent payments.

Trends over time

Where possible, trends are provided over time. Trends are provided back to the 1991 census for national crowding; for other indicators, a comparison is made where possible with 2006 census data.