New Zealand’s population is continually changing - the number of births is currently at levels last seen in the early 1960s - life expectancy has never been as high, meanwhile we have changing migration patterns. These are just some of the demographic data released by Statistics NZ in recent months.
Statistics NZ also produces population projections and these have come under the spotlight recently as an upsurge in births has surprised many.
“What we tend to find is that at least one of the components of population change is in a state of flux,” says demographic analyst Richard Speirs.
Births have increased by 11 percent from 57,700 in 2005 to 64,300 in 2008. Increasing birth rates for women at all childbearing ages underlie this increase. Notably, birth rates have risen among women aged 15–29 years, while previously they had been falling.
The increase since 2005 is not just confined to New Zealand; birth rates are increasing in several OECD countries, including Australia and the United Kingdom.
“While the upswing in births probably reflects changes in the timing of births rather than a profound shift to larger family sizes, it is difficult to pinpoint reasons for the sudden increase,” Richard says.
The current population projections were derived in 2007 when birth numbers and birth rates had only just begun their most recent upswing. The projections indicated an increase in births beyond 2007, although the extent of the increase varied between projection series.
“Actual birth numbers have certainly been at the high end of the projected range. The mistake that some users of the projections make is to interpret the mid-range projection as an actual prediction,” Richard says.
“We produce several projection series because the future is uncertain. It would be irresponsible of us to produce just one projection, as this would imply a certain future.”
Future mortality and migration are also uncertain. Life expectancy at birth continues to increase but there is no consensus internationally as to what it can, or will, reach. Meanwhile, net migration can fluctuate significantly over short periods of time.
Since 1951, New Zealand has experienced net permanent and long-term migration ranging between a net outflow of 43,300 in the year ended June 1979 and a net inflow of 42,500 in the year ended June 2003.
“Despite fluctuations, recorded deaths and net migration in 2007–09 are similar to the mid-range projection, and well within the range provided by the alternative projections.”
Statistics NZ releases updated projections every two to three years to incorporate the latest demographic trends. Projections assist in planning for the future. Information about the future size and structure of the population helps government and communities to plan infrastructure and facilities to meet the needs of a changing population.
For example, the recent increase in births will affect the number of school entrants within five years. New classrooms or even new schools will be needed if birth rates remain at their current levels. Whether the short-term increase in birth rates affects average family size in the long term, however, is unclear.
“For users of projections, an implication of these variations is not to rely on a single projection as a forecast. Alternative projections are produced for conveying uncertainty and alternative population and birth outcomes,” Richard says.
For more information contact: demography@stats.govt.nz.