Business » Enterprise & Development 1. A sociological concept that describes changes in families across time. Emphasis is placed on the effects of marriage, divorce, births, and deaths on families and the changes in income and consumption through various family stages. 2. Families account for a very large percentage of all consumer expenditures. Much of this spending is systematic and stems from natural needs that change as a family unit goes through its natural stages of life. These range from the young single and the newly married stages to the full nest as the children are born and grow, to the empty nest and the final solitary survivor stage. Each transition prompts changes in values and behaviour.