Housing quality: dwelling dampness, mould, and access to basic amenities (information about this variable and its quality)

Description

Housing quality

Housing quality refers to the adequacy of the structure (internal and external) and internal environment of a dwelling.

Good quality housing is housing that is suitable for habitation. It provides sufficient shelter and protection from the outside environment, a healthy indoor environment (warm, safe, mould free, and dry), and contains the amenities needed for everyday living.

  • amenities are services and structures such as electric lighting, drinkable water, bath or shower, toilet, and kitchen/cooking facilities
  • dampness of a dwelling is measured by if it is always damp, sometimes damp or not damp
  • presence of mould is defined by how much mould is present in a dwelling by measuring the size eg mould over A4 size.

An official definition of housing quality was published in 2019.

There are also separate definitions for the individual housing quality variables being collected in the 2018 Census:

Dwelling dampness indicator

Dwelling dampness indicator indicates whether an occupied private dwelling is not damp (dry throughout) or the degree to which it is damp, sometimes damp, or always damp. Dampness is defined as when a dwelling feels or smells damp or has damp patches on the wall, ceiling, floor or window frames.

Dwelling mould indicator

Dwelling mould indicator provides a measure of the total amount of visible mould inside occupied private dwellings. It indicates whether there is mould present that has a total area larger than an A4 sheet of paper, or whether the total amount present is smaller than A4 size, or there is no mould. It excludes any mould that is not visible (eg mould inside walls).

Access to basic amenities

Access to basic amenities indicates what basic amenities (eg cooking facilities, shower or bath, and electricity) are available inside an occupied private dwelling. The amenities need to be in working order to be counted.

Statistics

Representation

Variable Details

Other Variable Information

Housing quality variables

  • Dwelling dampness indicator
  • Dwelling mould indicator
  • Access to basic amenities
  • Number of basic amenities available

Priority level

Priority level 3

We assign a priority level to all census variables: Priority 1, 2, or 3 (with 1 being highest and 3 being the lowest priority).

Housing quality is a priority 3 variable. Priority 3 variables do not fit in directly with the main purpose of a census but are still important to certain groups. These variables are given third priority in terms of quality, time, and resources across all phases of a census.

Housing quality is a new topic area in the 2018 Census.

Quality Management Strategy

Overall quality rating for 2018 Census

Moderate quality

Data quality processes section below has more detail on the rating for this variable.

The External Data Quality Panel has provided an independent assessment of the quality of these variable and has rated them as moderate quality. 2018 Census External Data Quality Panel: Assessment of Variables has more information.

Subject population

Occupied private dwellings

‘Subject population’ means the people, families, households, or dwellings to whom the variable applies.

How this data is classified

Census dwelling dampness indicator V2.0.0

Dwelling dampness indicator is a flat classification with the following categories:

01 Always damp

02 Sometimes damp

03 Not damp

99 Not elsewhere included

‘Not elsewhere included’ contains the residual categories of ‘don’t know’, ‘response unidentifiable’ and ‘not stated’.

Census dwelling mould indicator V2.0.0

Dwelling mould indicator is a flat classification with the following categories:

01 Mould over A4 size – always

02 Mould over A4 size – sometimes

03 No mould/mould smaller than A4 size

99 Not elsewhere included

‘Not elsewhere included’ contains the residual categories of ‘don’t know’, ‘response unidentifiable’ and ‘not stated’.

Census access to basic amenities V2.0.0

Access to basic amenities is a flat classification with the following categories:

0 None of these

1 Cooking facilities

2 Tap water that is safe to drink

3 Kitchen sink

4 Refrigerator

5 Bath or shower

6 Toilet

7 Electricity supply

9 Not elsewhere included

‘Not elsewhere included’ contains the residual categories of ‘response unidentifiable’ and ‘not stated’.

Access to basic amenities is a multiple response variable. Therefore the total number of responses in a table is greater than the total occupied private dwellings stated.

Census number of basic amenities available V2.0.0

Number of basic amenities available is a flat classification with the following categories:

0 No basic amenities available

1 One amenity

2 Two amenities

3 Three amenities

4 Four amenities

5 Five amenities

6 Six amenities

7 Seven amenities

9 Not elsewhere included

‘Not elsewhere included’ contains the residual categories of ‘response unidentifiable’ and ‘not stated’.

If desired, the ‘always’ and ‘sometimes’ categories for mould and damp can be grouped together for output to provide more summarised information. Some of the individual number categories for number of basic amenities can be grouped into ranges (for example none, one–three, four–five, six, seven) to provide more summarised information.

Output can be produced for all occupied private dwellings or restricted to households in private occupied dwellings, as required.

Output that counts people rather than dwellings or households can be produced to allow analysis of housing quality together with personal characteristics such as age group.

The Standards and Classifications page provides background information on classifications and standards.

Question format

Dwelling dampness indicator is collected on the dwelling form (question 14 on the paper form).

Dwelling mould indicator data is collected on the dwelling form (question 15 on the paper form).

Access to basic amenities is collected on the dwelling form (question 16 on the paper form).

Number of basic amenities available is derived from access to basic amenities on the dwelling form (question 16 on the paper form).

Stats NZ Store House has samples for both the individual and dwelling paper forms.

There were differences between the wording or question format in the online and paper versions of these questions.

  • The paper dwelling form, question 15 - dwelling mould indicator, included the note ‘An A4 sheet is the size of 1 page of this 4-page form’, to help respondents answer the question. This was not included on the online form.

There were also differences in the way a person could respond:

On the online dwelling form:

  • for the damp and mould questions, only one response could be selected
  • it was not possible to mark ‘none of these’ and one or more of the amenities boxes. If ‘none of these’ was marked, all other responses disappeared.

On the paper dwelling form:

  • for the damp and mould questions, it was possible to select more than one response
  • for the amenities question, it was possible to select none of these and one or more of the amenities boxes.

These responses were resolved using edits.

How this data is used

Outside Stats NZ

  • To enable better understanding of the state of New Zealand’s housing.
  • To create direction and initiatives to address housing quality issues and assist with community development work.
  • To strengthen the case for attention to this health determinant, inform public health action, and help with targeting resources for maximum benefit.
  • To feed into legislative requirements of councils.
  • For civil defence and emergency management.
  • For measuring the full extent of severe housing deprivation in New Zealand.

Within Stats NZ

  • To produce more in-depth reports and analysis on housing.

2018 data sources

The tables below show that there were no alternative data sources or imputation used to replace missing responses or responses that could not be classified for the housing quality variables.

2018 dwelling dampness indicator –
occupied private dwellings
Source Percent
Response from 2018 Census 92.0 percent
2013 Census data 0.0 percent
Administrative data 0.0 percent
Statistical imputation 0.0 percent
No information 8.0 percent
Total 100 percent
Due to rounding, individual figures may not always sum to the stated total(s)  
2018 dwelling mould indicator – occupied private dwellings
Source Percent
Response from 2018 Census 91.9 percent
2013 Census data 0.0 percent
Administrative data 0.0 percent
Statistical imputation 0.0 percent
No information 8.1 percent
Total 100 percent
Due to rounding, individual figures may not always sum to the stated total(s)  
2018 access to basic amenities (total responses) – occupied private dwellings
Source Percent
Response from 2018 Census 92.0 percent
2013 Census data 0.0 percent
Administrative data 0.0 percent
Statistical imputation 0.0 percent
No information 8.0 percent
Total 100 percent
Due to rounding, individual figures may not always sum to the stated total(s)  

The ‘no information’ percentage is where we were not able to source housing quality data for a dwelling in the subject population.

Missing and residual responses

‘No information’ in the data sources tables, is the percentage of the subject population coded to ‘not stated’.

2018 percentage of ‘not stated’ for occupied private dwellings:

  • dwelling dampness indicator: 8.0 percent
  • dwelling mould indicator: 8.1 percent
  • access to basic amenities: 8.0 percent.

Responses that could not be classified or did not provide the information asked for such as ‘response unidentifiable’ and ‘don’t know’ remain in the data. In the 2018 housing quality data sources tables, these residuals are included in the ‘Response from 2018 Census’ percentage.

For output purposes, these residual category responses are grouped with ‘not stated’ and are classified as ‘not elsewhere included’.

2018 percentage of ‘not elsewhere included’ for occupied private dwellings:

  • dwelling dampness indicator: 11.0 percent
  • dwelling mould indicator: 10.3 percent
  • access to basic amenities: 8.1 percent.

2013 Census data user guide provides more information about non-response in the 2013 Census.

Data quality processes

Overall quality rating:

  • dwelling dampness indicator – moderate quality
  • dwelling mould indicator – moderate quality
  • access to basic amenities – moderate quality.

Data was evaluated to assess whether it meets quality standards and is suitable for use.

Three quality metrics contributed to the overall quality rating:

  • data sources and coverage
  • consistency and coherence
  • data quality.

The lowest rated metric determines the overall quality rating.

Data quality assurance for 2018 Census provides more information on the quality rating scale.

Data sources and coverage:

  • dwelling dampness indicator – moderate quality
  • dwelling mould indicator – moderate quality
  • access to basic amenities – moderate quality.

We have assessed the quality of all the data sources that contribute to the output for these variables. As no alternative data sources or imputation were used to replace missing responses, the final data sources and coverage quality rating for these housing quality variables reflects the lower than expected response to the census overall and the high proportion of admin enumeration.

The rating for a valid census response is defined as 1.00. Ratings for other sources are the best estimates available of their quality relative to a census response. Each source that contributes to the output for that variable is then multiplied by the proportion it contributes to the total output. The total score then determines the metric rating according to the following range:

  • 98–100 = very high
  • 95–<98 = high
  • 90–<95 = moderate
  • 75–<90 = poor
  • <75 = very poor.

The proportion of data from received forms contributed to the following scores for the housing quality variables, determining their moderate quality rating:

  • dwelling dampness indicator – 0.92
  • dwelling mould indicator – 0.92
  • access to basic amenities – 0.92.
Quality rating calculation table for the sources of dwelling dampness indicator
– 2018 occupied private dwellings
Source Rating Percent of total Score contribution
2018 Census form 1.00 91.97 0.92
No Information 0.00 8.03 0.00
Total 100.00 0.92
Due to rounding, individual figures may not always sum to the stated total(s) or score contributions.      
Quality rating calculation table for the sources of dwelling mould indicator – 2018 occupied private dwellings
Source Rating Percent of total Score contribution
2018 Census form 1.00 91.93 0.92
No Information 0.00 8.07 0.00
Total 100.00 0.92
Due to rounding, individual figures may not always sum to the stated total(s) or score contributions.      
Quality rating calculation table for the sources of access to basic amenities – 2018 occupied private dwellings
Source Rating Percent of total Score contribution
2018 Census form 1.00 92.03 0.92
No Information 0.00 7.97 0.00
Total 100.00 0.92
Due to rounding, individual figures may not always sum to the stated total(s) or score contributions.      

Consistency and coherence:

  • dwelling dampness indicator – high quality
  • dwelling mould indicator – high quality
  • access to basic amenities – high quality.

Housing quality data is mostly consistent with expectations across nearly all consistency checks. There is an overall difference in the data compared with expectations and benchmarks that can be explained due to real-world change.

As these are new variables, there is no available census data for comparison. Consistency and coherence were assessed by comparing the census results with the General Social Survey (GSS) and by cross-tabulating this data with other variables for example tenure of household and the New Zealand Deprivation Index 2013 (NZDep13). These comparisons and checks showed the expected patterns.

Data quality:

  • dwelling dampness indicator – high quality
  • dwelling mould indicator – high quality
  • access to basic amenities – high quality.

The data quality checks for these housing quality variables included edits for consistency within the dataset and cross-tabulations to the regional council level.

Housing quality data has only minor data quality issues. The quality of coding and responses within classification categories is high. Any issues with the variables appear in a low number of cases (typically in the low hundreds).

For dampness and mould, the level of ‘don’t know’ and unidentifiable responses was low. The level of unidentifiable responses was also low for access to basic amenities.

Visible mould may be easier to report than dampness. There may be a small amount of under-reporting of dampness in this data because some people may be unaware of dampness in their home.

Recommendations for use and further information

When using this data you should be aware that:

  • data has been checked to regional council level. Some variation is possible at geographies below this level
  • there were severe weather events, including a cyclone, around the time of the 2018 Census. This may have affected reporting of access to drinkable tap water
  • the timing of data collection can affect how people respond to questions on dampness and mould. The early March timing of the census may reduce reports of dampness and mould and increase responses of ‘don’t know’ by respondents who have moved recently and have not yet experienced a winter in their current home.
  • because non-private dwellings have been excluded, this data does not provide any indication of housing quality issues with boarding houses or other types of non-private dwellings in which people may live.

Contact our Information Centre for further information about using this variable.

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