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3.3  Migration

During the 1990s, levels of net migration into New Zealand were comparable to those following World War II, in contrast to the dramatic outflows of the early 1970s and 1980s (Figure 7). Immigration regulations have long favoured young working-age migrants (Statistics New Zealand 2002b: ). In-migration does in fact peaks around these age groups, though, as Figure 8 shows, so does out-migration.

Figure 7 – Net migration to New Zealand (thousands)
Net migration to New Zealand (thousands)
Source: Statistics New Zealand 2002b: Table 5.16.

Note – These estimates are for total migration, and do not distinguish between “permanent and long-term” and “short-term” migrants.

Higher levels of in-migration tend to increase the proportional share of the working ages and reduce the dependency ratio. However, the magnitude of these increases is typically less than intuition would suggest. Despite the peaks around the young working ages, many migrants belong to older age groups. Even those in-migrants who are young when they arrive grow old themselves, and have children, thus contributing towards the number of dependants.

Figure 8 – Permanent and long-term migration by age, 2001 and 2002: year to June 2001 (left) and year to June 2002 (right)
Permanent and long-term migration by age, 2001 and 2002
Source: Statistics New Zealand (2002a: Table 5.4).
Figure 9 – Statistics New Zealand 2001-base projections for the total dependency ratio, with varying migration assumptions
Statistics New Zealand 2001-base projections for the total dependency ratio, with varying migration assumptions
Source: Data accessed from Statistics New Zealand website www.stats.govt.nz in July 2003.

Note – Both projection series assume “medium” fertility and “medium” mortality; the “0 migration” series assumes net migration of 0 per annum, and the “20,000 migration” series assumes net annual migration of 20,000.

The most satisfactory way to analyse these processes would be to set up a simulation that, for instance, distinguished between students and longer-term migrants, distinguished New Zealand citizens from non-citizens, and allowed migrants to have different fertility rates from non-migrants. This is not currently possible, given available data. Some insights can, nevertheless be gained by comparing results from conventional projection series based on varying assumptions about migration.

Figure 9 compares results from two of Statistics New Zealand’s 2001-base projection series. The two series both use the medium’ fertility and ‘medium’ mortality assumptions. The first series uses Statistics New Zealand’s ‘0 migration’ assumption, which is the assumption with the lowest long-term level for net migration. Under this assumption, in-migration exactly matches out-migration after a short adjustment period—though for the population as a whole, and not for every age group. The second series uses Statistics New Zealand’s “20,000 migration” assumption, which is the assumption with the highest long-term level for net migration. Under this assumption, in-migration eventually exceeds out-migration by 20,000 per year. Over 50 years, a difference of 20,000 per year adds up to 1 million extra migrants, a substantial number. As can be seen in Figure 9, dependency ratios are indeed lower under the “20,000 migration” scenario. The reduction is not, however, large: 0.65 dependants per working-age person by 2051 rather than 0.71. The effect on population size is large. The population in 2051 would be 5.8 million under the “20,000 migration” assumption and only 4.4 million under the “0 migration” assumption (the difference is greater than 1 million mainly because of births to migrants.)

Similar exercises have produced similar results in other countries (United Nations 2000, Young 1988). It seems to be a general rule that migration has a much larger impact on population size than it does on population age structure.

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