To compare the standards of living of households of different sizes or compositions, we divide the income by the number of consumption units (CU). These are usuallly calculated the following way:
- 1 CU for the first adult in the household,
- 0.5 CU for the other persons aged 14 years or older,
- 0.3 CU for the children under 14 years.
This scale (known as the OCDE scale) takes the economy of scale inside the household. Indeed, the needs of the household do not increase proportionally to its size.
When several people live together, it is not necessary to multiply all the consumer goods (in particular durable consumer goods) by the number of people in order to keep the same standard of living.