Time poverty should therefore be understood as a lack of discretionary time once needs have been met (or the time potentially available for people to do what they want), and standards should be defined as the amount of time strictly necessary for people to perform the unavoidable activities of daily life (paid and unpaid work, personal care and others). Vickery (1977) argues that thresholds should be built taking into account household composition and habits of eating, household management and purchase of goods. Given the lack of established standards, Burchardt (2008) used an operating definition based on the behaviour of a reference group, taking minimum time spent on domestic work to be the average time spent on those tasks by households around the poverty line which do not receive state assistance and do not pay for domestic services on the market.