Quintiles

A statistical value of a data set that represents 20% of a given population. The  first quartile represents the lowest fifth of the data (1-20%); the second  quartile represents the second fifth (21% - 40%) etc.

Quintiles are often used to create cut-off points for a given  population. For example, a government sponsored socio-economic study  may use quintiles to determine the maximum wealth a family could possess in  order to belong to the lowest quintile of society. This cut-off point can  then be used as a prerequisite for a family to receive a special government  subsidy aimed to help society's less fortunate.