Ethnic counts on mortality and census data 2001-06: New Zealand census-mortality study update.

AIM

To provide an update for the assessment of discrepancies in ethnicity counts in the 2001 census and mortality data for the 2004-2006 period.

METHODS

2001 census anonymously and probabilistically linked to 5 years of subsequent mortality data (135,849 eligible mortality records), allowing a comparison of ethnicity recording for the years 2001-2004 and 2004-2006.

RESULTS

Using a total definition of ethnicity, census and mortality counts agree reasonably well in 2004-06 and resemble comparisons in 2001-04, except at younger ages where counts for Pacific and Asian ethnicities are up to a third less for mortality data. Due to multiple ethnicities being more commonly recorded on census data, sole ethnicity counts are generally greater on mortality than census data, particularly for Maori ethnicity.

CONCLUSION

Similar to 2001-2004, there is little bias in ethnic group counts between census and mortality data when using total ethnicity. Calculations of mortality rates by ethnicity using unlinked census and mortality data and a total definition of ethnicity should be unbiased. These results support ongoing use of the census definition of ethnicity on all health datasets.