For developing countries, it is based on the evolution of absolute poverty (i.e. the proportion of population living on less than $1 a day). For developed countries, poverty is measured as relative income poverty (i.e. with the threshold set as a percentage of the median income in each countty in each of the years considered). Only a few OECD countries have “official” measures of poverty that rely on “absolute" standards, typically in the form of the cost of a basket of goods and services required to assure minimum living conditions and indexed for price changes over time.