These summary graphs show population numbers by age (top panel), net migration number by age (middle panel) and net migration as a percentage of the base population by age (lower panel). The ‘base population’ is the population of the same age at the start of each decade. See for underlying methodology.

Graphs where population numbers are small will tend to be ‘messy’ and viewers may not see any clear picture emerging. However, where numbers are sufficient, the top panels provide a clear illustration of the process of population ageing, where numbers at the youngest ages were highest (or near-highest) in 1976 and have fallen since, and numbers at older ages are successively higher at each successive census. The picture is somewhat different where areas have grown significantly across all ages, such as Rolleston. The graph is a type of ‘population pyramid’.

The middle and lower panels showing net migration numbers and rates by age tend to show fairly consistent patterns over time, at least where numbers are not too small. Most graphs show migration concentrated among the younger age groups—see for example Dunedin, Palmerston North and Wellington, which have among the most consistent migration age profiles of this type. Fewer have migration concentrated to the right, where there is a lot of migration around retirement age—see for example Paeroa, Pauaunui Beach, Thames, Waihi Beach, Warkworth and Winton.

Where there is net gain (or loss) across the main parental age groups (25-54 years) there is usually a concomitant gain (or loss) at age 0-14 years; Rolleston and Tauranga are good examples of gains at these ages; Westport, Turangi and Taumarunui of loss; Whangarei and Taupo of earlier loss and recent gain. Overall, most areas show a net loss at 15-19 and/or 20-24 years, while university towns (like Palmerston North and Hamilton) tend to show net gain at 15-24 years and a net loss at 25-29 years.

These patterns and trends can be understood in more detail by examining the graphs by broad age group (see Change by Component Graphs).