3.1 Income for whom?
Income may be measured at either the individual or household level.
As the members of a household usually pool their resources, measuring income at the household level may be more indicative of living standards for the household as a whole.
For example, if there is a stay-at-home parent in a household their income may be very low or non-existent. However, their partner may receive a high income such that they experience a relatively high standard of living in their household.
But there may also be inequality within a family: household income level does not guarantee that income is distributed equally among the members of a household.