Calculations of life expectancy and rates of death by disease rely on the collection and analysis of health records and census data, and registrations of births and deaths. These records are not always reliable, so their use to indicate trends is sometimes debated by experts in this field. They are, however, essential to an understanding of population changes.
The British passion for collecting and interpreting population statistics was brought to New Zealand from the 1840s by European settlers. In 19th-century Britain, there was great enthusiasm for identifying health and social trends, and quantifying death rates.
In England, national registration of births and deaths began in 1837. For death records, the person’s age and gender were recorded, and soon the cause of death was included as well. Dr William Farr helped develop this official data system and was the first to use it to analyse death statistics extensively. His basic statistical methods were still in use in the early 21st century.
The most powerful technique for analysing mortality was the life table, a tool dating from the 17th century. In life tables, records of birth and death rates were subjected to a formula to calculate life expectancy at particular times. By the late 19th century these tables were being computed in ways that resemble state-of-the-art practices in the 21st century.
Using population statistics, Farr identified what he called ‘healthy districts’, which tended to be rural areas. Cities were seen as overpopulated and filthy, and therefore unhealthy. Colonies such as New Zealand were regarded as distant healthy districts, so statistics about their inhabitants were of interest in Britain for comparative purposes.
New Zealand settler records
In New Zealand, Pākehā births and deaths were officially recorded from 1848, and from 1875 fuller information about the person and their cause of death was collected for death certificates. By the 1870s virtually all Pākehā deaths were registered, so by that time the records could be usefully analysed. Only since the later 20th century, however, has the cause of death been described well enough to interpret fully.
From the 19th century, strenuous efforts were made by missionaries, travellers, physicians, district magistrates and census enumerators to record Māori population and health statistics. Official Māori birth and death records were kept from 1913. Despite these attempts, registration of Māori births and deaths did not occur reliably until after the Second World War. However, techniques to analyse populations with incomplete data can be applied to reconstruct Māori population history back to the 19th century.