As the estimates refer to the number of people in the population at 30 June each year, the statistics are often referred to as the mid-year estimates. They are updated using a standard technique known as the cohort component method. In simple terms,the previous year’s population estimate is “aged on” by one year, with births added and deaths removed. Net migration is also accounted for. In 2011 the Census population was the basis for the mid-year estimates.