The main cause of rapid population growth is when there are more births than there are deaths, which is referred to as a natural increase. Other causes of rapid population growth include an increase in food production and distribution, improvement in public health and the elimination of many diseases.
An increasing number of individuals are choosing to live healthier lifestyles, which in turn has increased life expectancy rates, while regional population growth can be attributed to migration. In New Zealand, migration accounts for approximately two-thirds of the region’s population growth. Some regions send more migrants to other areas than they receive, so the result for those areas is a decrease in population.