8.2 New Zealand occupation datasets and the New Zealand Election Study data

Just as with income data, no official representative datasets are available at an individual level on the occupations of children's parents and of occupations of these children when they are adults. We have therefore used data from the New Zealand Election Study (NZES), which has been carrying out a voluntary nationally representative post-election survey of voters at all elections since 1990 (www.nzes.org/). These studies have resulted in the publication of five books on voting behaviour and in the publication of articles in international journals. Researchers have used the data for a variety of purposes. Although this is the first use of NZES data to study intergenerational mobility, intergenerational mobility in Britain has been studied using data from the British election study (Heath and Payne, 1999, p. 4).

Between 1990 and 1996, the NZES's post-election postal survey asked respondents what their occupation was, and what their parents' occupations had been when the respondent was aged about 14. Fourteen is the age used in similar overseas surveys and is a good age for establishing parents' usual occupation (Ermisch, et al., 2006, pp. 14-15; Leigh, 2007, p. 4). We use this data to study intergenerational mobility by using occupation to determine people’s SES, and then testing the relationship between respondents’ and their fathers’ SES.

Unfortunately, after 1996 the NZES did not ask about parents' occupation again until 2008, and the 2008 occupation data is not yet available. This limits the relevance of the results. Since the NZES dataset approximates a simple random sample, the concerns about inference from a population study discussed in Section 8.1.2 do not apply. However, the response rate of 55.7% for the mail survey, which was the only surveying method that asked about parents' occupations, may have affected the results. Although the response rate is high for a voluntary post-election survey, the response rate is also considerably lower than for the income questions in the Dunedin Study. Some researchers would criticise the use of significance tests and confidence intervals because of the Election Study's response rate (Henkel, 1976, p. 80). Section 3.2 discussed limitations of the SES data, such as how some of the SES groups contain people from a wide range of economic backgrounds. The following sections discuss in more detail how the 1996 Election Study dataset imperfectly mirrored New Zealand’s 1996 population and how this may have affected the results.

8.2.1  Sampling design and the representativeness of the sample

In 1996, the NZES post-election sample had three main components: the new sample; the panel study; and the campaign wave. The total number of responses was 5,012 (Table A5). Those interviewed over the telephone were not asked about their parents' jobs. The total sample available for our study is therefore the 4,118 mail responses.

The new sample was a random sample of voters drawn from the 1996 general and Māori electoral rolls. People are usually qualified to enrol to vote in New Zealand if they are 18 years or older, are New Zealand citizens or permanent residents and have lived in New Zealand for one year or more without leaving the country. New Zealand is unusual because it allows non-citizens to vote if they are permanent residents (Nagel, 1988, pp. 17-18). Enrolment usually lapses only if a citizen has been out of New Zealand continuously for three years or more (with some exemptions), or if a person is in prison for a term of three or more years (New Zealand Government, 1993, section 80). No data is available for 1996, but in the late 1980s less than one percent of people over 18 living in New Zealand were unable to vote because of the eligibility rules (Nagel, 1988, pp. 17-18).

About 91.6% of eligible voters (those who were legally entitled to vote) were on the electoral roll in 1996 (New Zealand Post, 1997, p. 29). Eligible voters are legally required to enrol in New Zealand, although efforts to increase enrolment concentrate on publicity and on education campaigns (Elections New Zealand, 2009; Electoral Enrolment Centre, [2008], pp. 8-11). Groups that are less likely to be on the roll include those who move frequently, young people, people who are travelling overseas, new citizens, Māori and Pacific and Asian peoples. Some people are also reluctant to enrol because the electoral roll is publicly available (apart from an unpublished roll for people who can prove that publication of their name and address would place their safety at risk). The electoral roll can therefore be used by people, such as debt collectors, to find addresses (Electoral Enrolment Centre, [2008], p. 10; Electoral Law Committee, 1998, pp. 26-33; Jackson, 1996, p. 14).

People of Māori descent enrolling for the first time can choose the Māori or general roll. Thereafter they can only decide during the Māori Electoral Option that follows each five-yearly census. The NZES's new random sample included a deliberate oversample of voters on the Māori electoral roll to improve knowledge of Māori electoral behaviour. Following the 1994 Māori Electoral Option, about 52% of people of Māori descent were on the Māori electoral roll. Coverage was lower in the South Island where only 39% of people of Māori descent were on the Māori electoral roll (Statistics New Zealand, 2006). In addition to the deliberate oversample of voters from the Māori electorates, the NZES also surveyed people of Māori ancestry and identity through the other study samples.

The second component of the 1996 post-election sample was a panel study of people who had been part of the 1990 and/or 1993 Election Study and who had agreed to also be part of the 1996 Election Study. Originally this sample had been drawn from the 1990 and 1993 electoral rolls.

The third component of the 1996 post-election sample was the campaign wave of people who had been surveyed by telephone before the election and who had agreed to give their address so that they could be sent a post-election survey. This part of the sample captured an unknown number of adults who were not on the electoral roll. The number of respondents in this category is thought to be very small (Vowles, 2002a, p. 600). In 1996, 95.1% of New Zealand households had a telephone, with ownership being lowest among low-income groups, among Māori and among Pacific peoples (Statistics New Zealand, 1998b, pp. 16-17). Less than 5% of households who may have contained eligible voters were therefore outside the scope of the telephone survey.

The 1996 post-election survey was predominantly a mail survey. However, sample members who had failed to reply after two postal reminders were contacted by telephone (when their telephone number could be found) and asked to complete a shortened version of the survey over the telephone (Vowles, Aimer, Banducci and Karp, 1998, p. xiii). Unfortunately the post-election telephone survey did not include questions on parents’ occupations.

The mail respondents formed the basis of our sample for analysis. Although the mail response rate of 55.7% was high by international standards, there is considerable scope for non-response bias to affect analysis based on this data. We used the mail survey weight (mmqwt) provided with the data, which ensures the data matched voting behaviour. However, the data imperfectly matches some characteristics of New Zealand's population.

8.2.2  Data on Māori and the representativeness of this data

Intergenerational mobility of Māori is of interest to this study because Māori are New Zealand's indigenous people and are the largest component of the population after New Zealand European/Pākehā. The 1996 Election Study was New Zealand's first systematic survey-based study of Māori based on a national sample drawn from the electoral roll (Vowles, et al., 1998, p. xiii).

Whereas official statistics now use cultural self-identity to define who is Māori, most statutes use ancestry. Māori communities often consider Māori to be those who both have Māori ancestry and who self-identify as Māori. Other variables sometimes used to measure Māori identity include participation in Māori cultural activities, knowledge of Māori ancestry and use of the Māori language (Kukutai, 2004, pp. 90, 91, 94-95; Statistics New Zealand, 2005, p. 2).

We used the NZES's ethnic identity question to identify Māori. We included those who identified solely as Māori and also those who identified as Māori and another group. In total, 695 respondents identified as Māori, and this group comprised 13.5% of the NZES's weighted sample who responded by mail. This compares to 14.5% of New Zealand's population who identified as Māori in the 1996 census. However, the NZES asked for the ethnic group people mainly identified with, whereas the census asked people to “Tick as many circles as you need to show the ethnic group(s) you belong to” (Statistics New Zealand, 1996, 1998a). Most Māori in the NZES’s dataset circled only that they were Māori. Nevertheless, 54 respondents indicated that they identified as both European and Māori, and eight identified as both Māori and Pacific Islanders.

Almost all respondents who had indicated that they identified as Māori were of Māori ancestry, with 95.5% circling that they had some New Zealand Māori ancestry and another 2.8% indicating that they were unsure. The remaining 1.7% (11 respondents) circled that they had no Māori ancestry. However, three of these 11 respondents were on the Māori electoral roll, showing that they had ticked that they were “a descendant of a New Zealand Māori” when they had enrolled (Electoral Enrolment Centre, 2009). Of the 18 respondents who identified as Māori but were unsure if they had Māori ancestry, 16 were also on the Māori electoral roll. People’s answers to survey research rarely generate completely compatible answers, with people often answering questions quickly and changing their answers over time, in response to question wording and according to the context. But our data indicates that almost everyone who identified as Māori had indicated that either they had Māori ancestry in the survey, or were unsure of whether they had Māori ancestry, or had indicated that they were of Māori descent when they had enrolled to vote.

Of those who had Māori ancestry, 66.6% identified themselves as New Zealand Māori. The next most common ethnic identifications among those with some Māori ancestry were New Zealand European (21.0%) and Pākehā (5.3%). The Election Study ethnicity question discouraged multiple answers, which may have affected the results.

Among respondents who identified themselves as Māori, 544 were on the Māori electoral roll while 151 were on the general electoral roll. In the NZES's 1996 weighted sample 59.2% of those of Māori ancestry were on the Māori roll compared to Statistics New Zealand's calculation of 52% of those of Māori descent in 1994 (Statistics New Zealand, 2006, p. 26). This suggests a slight bias in the NZES data towards Māori on the Māori roll, although Māori enrolling for the first time may have disproportionately chosen the Māori roll. At the time of the 1994 Māori enrolment option, some Māori organisations were actively encouraging Māori to choose the Māori roll by claiming that this would increase Māori political representation and power (Kia Hiwa Ra, 1994, p. 5). Different question wording may have also affected the results. The NZES’s researchers admitted that the age distribution of the study’s Māori respondents differed from that of the electoral roll, with the sample under-representing 18-29 year-olds and over-representing 30-39 year-olds (Sullivan and Vowles, 1998, pp. 190-191).

Māori language use is a key aspect of Māori ethnic identification (Kukutai, 2004, p. 91). In the Election Study dataset, 48.3% of those who identified as Māori wrote that they spoke Māori at home, compared to just 1.1% of the rest of New Zealand’s population. 63.7% of Māori on the Māori electoral roll wrote that they spoke Māori at home compared to 16.4% of Māori on the general electoral roll.