The size of households in general follows the life-cycle of families. Households are usually small at the stage of relationship formation (early marriage), and then increase in size with the advent of children. They later reduce in size again as these children reach adulthood and leave home. Household size can also be influenced by a lack (or abundance) of affordable housing. Overseas migrants and indigenous persons often have a tradition of living with extended family members which significantly affects household size.

Household size in Australia has generally declined since the 1970s, but the rate of decline has slowed in recent years.

An increasing household size in an area may indicate a lack of affordable housing opportunities for young people, an increase in the birth rate or an increase in family formation in the area. A declining household size may indicate children leaving the area when they leave home, an increase in retirees settling in the area, or an attraction of young singles and couples to the area.

For greater insight, Phillip Island's Household Size data should be viewed in conjunction with Household Summary, Age Structure, Dwelling Type, Household Income and Language Spoken at Home.