We utilised data from the first three waves (October 2002/03, 2003/04, 2004/05) of SoFIE (wave 1 to 3 data, Version 4) (Carter et al. 2008). SoFIE is a nationally representative fixed-panel longitudinal survey of the usually resident population living in private dwellings. The initial SoFIE sample comprised approximately 11,500 responding private households (response rate of 77%) with over 22,000 adults responding in wave 1, reducing to just over 20,000 in wave 2 (91%) and 18,300 in wave 3 (83% of wave 1 responders). In SoFIE, face-to-face interviews are used to collect information annually on demographics and the social and economic characteristics of adults.
In this analysis, data were restricted to adults (15 years or older) who answered the ethnicity question in all three waves.
The following ethnicity question was asked in each wave:
“Looking at showcard 7, choose as many responses as you need to say which ethnic groups you belong to.”
This ethnicity variable was then coded to the following level 1 categories: NZ European / Pākehā, Māori, Pacific, Asian, and Other.
For the purposes of this paper we constructed four variables relating to ethnicity.
Total ethnicity. For simple cross-classifications we simply used the total counts of people identifying as Māori, Pacific, NZ European, Asian or “Other”. Note that the sum of the total counts will exceed 17,625 (total number of responding adults) due to people reporting two or more level 1 ethnic groups (total ethnic groups are not mutually exclusive).
Combination ethnicities I. We categorised people (at each wave) into those reporting just one level 1 ethnic group (“sole”), and two or more level 1 ethnic groups (“multiple”). Note that someone who self-identified with more than one Pacific or Asian ethnicity appears as “sole” using the level 1 categorisations in this paper.
Combination ethnicities II. We also constructed variables separately from the perspective of each of the level 1 groups. Thus, from the Pacific perspective one could be sole Pacific, Pacific plus at least one other group, or non-Pacific (any other ethnic group/s excluding Pacific).
Changing ethnicity. We classified anyone changing their self-identified ethnic group between waves 1 and 2 or between waves 2 and 3 as “change”. Respondents may “change” their self-identified ethnicity by adding or subtracting an ethnic group to/from their previous wave response (e.g. Pacific and NZ European in wave 1, and sole Pacific in wave 2 = “change”), or responding with a totally different category (e.g. sole Māori in wave 1 and sole NZ European in wave 2 = “change”).
The following demographic, social and economic variables have been used to explore the mechanisms discussed previously and their relationship with changing ethnic identification over the three waves of SoFIE. The following demographic characteristics were measured at the wave 1 interview: age, sex, legal marital status, family structure and household composition. It is hypothesised that younger populations are more likely to change their ethnicity because they are developing their own identity as they grow older. Marital status, family structure and household composition are used to investigate the influence of social mechanisms on changing ethnicity. Economic variables allow us to investigate whether changing ethnicity is more apparent in some social and economic groups. Household income was derived by totalling adult annual personal income (before tax) from all sources received, Consumer Price Index adjusted, equivalised for household economies of scale using a New Zealand-specific Jensen Index (Jensen 1988), and categorised into quintiles based on the SoFIE population across waves 1 to 3. Labour-force involvement was defined as being either employed, not employed but seeking work, or not employed and not seeking work, at the time of the interview. The highest level of education was coded as no education, school, post-school vocational, or degree or higher qualification, across the three waves. The New Zealand Deprivation (NZDep2001) Index provides a neighbourhood-level (approximately 100 people) deprivation score (Salmond and Crampton 2002). The global self-rated health question (“In general would you say your health is excellent, very good, good, fair or poor?”) was classified as fair/poor versus remaining answers.
These analyses will provide a baseline for future analyses of SoFIE data (once more waves of data are available) looking at the influences of changes in social and/or economic circumstances (i.e. moving from child to adult status, getting married or becoming unemployed) have on changes in self-identified ethnicity over time.
All analyses were conducted using SAS 8.2 within the Statistics NZ Data Lab, Wellington. Exploratory analysis was conducted using cross-tabulations to identify respondents who change ethnicity between the waves, by demographic and socio-economic variables. Logistic regression analyses were used to investigate the relative association of change in ethnicity by baseline socio-demographic variables.
All counts and values in the tables have been randomly rounded (up or down) to the nearest multiple of five, and cells with counts less than 10 were rounded to a minimum of 10. As a result, table totals may differ from the sum of individual cells. Some row percentages in the tables may also sum to greater than 100 because the percentages were calculated according to the random rounded totals.
A total of 17,625 original sample members aged 15 years or older at the wave 1 interview and who had responded in all three waves were included in this analysis. Table 1 presents the ethnic composition of the SoFIE population across the first three waves of SoFIE. Over 83% of the population reported NZ/European as one of their ethnic groups, with around 11% Māori, 5% Pacific, 5% Asian and 2% Other ethnicity. There is little variation in the share of the total ethnic groups in the population at each wave (although individuals are changing groups between waves, as shown below).
The majority of people (about 95%) reported that they affiliated with only one ethnic group (Table 1). This was stable over all three waves: 5.6% of people in wave 1 reported affiliating with more than one ethnic group, and in wave 3 this declined to 4.9%. The distribution of multiple affiliations was not equal: proportionately Māori (38.3%) and Pacific people (20.8%) were more likely to report affiliation with more than one ethnic group than NZ European (5.3%), at wave 3. About 10% of Asian and other ethnic groups reported multiple affiliations. Younger respondents were also more likely to report multiple ethnic groups.
Table Distribution of 17,625 SoFIE Respondents by “Sole” and “Multiple” Ethnic Groups
Level 1 ethnic group
* Total percentages are the proportional share of ethnic groups, by wave.
Stated ethnic group plus at least one other level 1 ethnic group.
Table 2 shows the distribution of characteristics of respondents who had any change in their self-identified ethnicity between waves 1 and 2 and waves 2 and 3. There was no difference between males and females, but younger respondents were much more likely to change ethnic groups (e.g. 12.2% for 15–24-year-olds compared to 2.7% for those aged 75 years and over).
The strongest predictor of changing ethnicity between waves was ethnicity at wave 1. Using a total definition of ethnicity at wave 1, anyone self-identifying as “Other” (ie, any ethnicity other than NZ/European, Māori, Pacific or Asian) was the most likely to change ethnicity between waves (54.7%), followed by Māori (36.5%), Pacific (22.9%), and Asian (15.4%). NZ/European respondents were least likely to change ethnicity across the three waves (5.7%).
Alongside considering “total” ethnicity at wave 1, changing ethnicity was most likely among those people recording two or more ethnic groups – regardless of the actual combination. People self-identifying at wave 1 as NZ European and any other group, Māori and any other group, Pacific and any other group and Asian and any other group all had similar probabilities (over half) of changing ethnicity between waves: 56.4%, 57.1%, 62.5% and 63.2%, respectively. Sole NZ/European were the least likely (2.4%), and sole Asian and sole Pacific both had about a 10% probability of subsequent change in ethnic group. Sole Māori, however, had a 21.3% probability of changing ethnicity over waves.
Table Distribution of the number of respondents reporting any change in ethnicity between waves 1 and 2 and waves 2 and 3, by wave 1 measures of socio-demographic characteristics
Considering other socio-demographic factors, there were moderate increases in the probability of changing ethnicity for those: not born in New Zealand, never married, living in a family with children (i.e. couple with children, or sole parent), and in good or fair/poor self-rated heath (Table 2). (It must be noted that these are all crude percentages, and likely to be confounded by age and ethnicity at least – hence the multivariable analyses below.) Finally, the crude analyses demonstrate two- to three-fold differences in the chance of changing ethnic groups for those with low income or living in a deprived neighbourhood.
Table 3 presents results from logistic regression models. The first column contains univariate regressions, which are consistent with the results in Table 2, aside from being on an odds ratio scale. However, any of the univariate associations attenuate once all factors are adjusted for in the multivariate analyses. Multivariate logistic regression analyses were conducted by each ethnic group at wave 1, both to investigate what factors influence changing ethnicity within the main ethnic groupings and also to overcome the problem of non-mutually exclusive ethnic groups.
Generalising across the four multivariate models, younger age, not being born in New Zealand, living in a family with children, living in a deprived neighbourhood, and having poorer self-rated health all tended to be moderate to strong predictors of changing ethnicity. Income and education had modest independent associations only. Considering the four ethnic multivariate models separately, that for NZ/European had instances of varying associations; most notably, country of birth was not associated with changing ethnicity.
Table 3 Odds Ratios (95% Confidence Interval) of any Change in Ethnicity across Waves 1 to 3 of SoFIE by Socio-demographics for Univariate and Multivariate Logistic Regression Analyses
Notes: Reference = not in that ethnic group. N = 17, 625.
Perhaps the key finding from the multivariate analyses was the persistent and strong association of wave 1 ethnicity with subsequently changing ethnicity. Allowing for the logistic model (i.e. odds ratios), the associations are broadly consistent with the results in Table 2 for simple proportions. For example, identifying with two or more self-identified ethnic groups at wave 1 is a consistently strong predictor of subsequent change in ethnicity. The model for a Māori-centric categorisation of ethnicity does, however, highlight the fact that sole Māori have a 7.7 greater odds of changing their self-identified ethnicity compared to non-Māori; sole groupings for the other three ethnicities did not have increased odds of changing ethnicity when compared with their counterpart “non” ethnic group.