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As we transition to our new site, you'll still find some Stats NZ information here on this archive site.

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Standards

Symbols

The interpretation of the symbols used throughout this report is as follows:

- nil or zero

-- amount too small to be expressed

.. figures not available

... not applicable

Confidentiality

The Statistics Act 1975 sets out strict requirements on Statistics New Zealand to protect the confidentiality of information obtained from respondents during the Census of Population and Dwellings and other surveys. All staff who work on the census and other surveys have signed a Declaration of Secrecy. In publishing statistical tables and other aggregated statistics from the census datasets, Statistics New Zealand employs measures such as random rounding to protect the confidentiality of individual information.

Random rounding

Since the 1981 Census, Statistics New Zealand has utilised a confidentiality assurance technique of randomly rounding census statistics to base three. This enables the greatest possible amount of census data to be released without compromising the privacy of individual responses. Under the random rounding process, all table cell values, including row and column totals, are rounded as follows:

  1. Zero counts and counts which are already multiples of three are leftunchanged.
  2. Other counts are rounded to one or other of the two nearest multiples of three.

All rounding, including separate rounding of totals and sub-totals is carried out on the recorded results. The probabilities of rounding up or down are set so that the long run expected value equals the original count. For example, an original count of 17 would be rounded to 15 with a probability of 1/3 and rounded to 18 with a probability of 2/3, since 15 x 1/3 + 18 x 2/3 = 17. The effect of this rounding on the accuracy of census statistics for practically any proposed use is insignificant.

Rounding procedures

On occasions, figures or percentages have been rounded off to the nearest unit or decimal point. This may result in a total disagreeing with the total of the individual items as shown in tables.

Calculation of ratios

Unless otherwise stated, the 'not stated' category has been excluded from the denominator in calculation of ratios and percentages.

Household calculations

Unless otherwise stated, the calculations in this report have been performed for households in private occupied dwellings.

 

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