In social statistics, income quintile groups are computed on the basis of the total equivalised disposable income attributed to each member of the household.
The data (of each person) are ordered according to the value of the total equivalised disposable income. Four cut-point values (the so-called quintile cut-off points) of income are identified, dividing the survey population into five groups equally represented by 20 % of individuals each:
- first quintile group of equivalised income;
- second quintile group of equivalised income;
- third quintile group of equivalised income;
- fourth quintile group of equivalised income;
- fifth quintile group of equivalised income.
The first quintile group represents 20 % of the population with the lowest income (an income smaller or equal to the first cut-off value), and the fifth quintile group represents the 20 % of population with the highest income (an income greater than the fourth cut-off value).