• Data reference period
• Place of residence (NUTS - 2013)

• REFERENCE PERIOD:  Period to which the information refers and which may be a specific day or a time interval (month, fiscal year, calendar year, among others).
• AGEING INDEX:  The ratio of the number of elderly persons of an age when they are generally economically inactive (aged 65 and over) to the number of young persons (from 0 to 14).
• RESIDENT POPULATION:  Set of persons who, regardless of being present or absent in a given housing unit at the moment of observation, have lived in the place of their usual residence for a continuous period of 12 months prior to the moment of observation, or have arrived to the place of their usual residence during the period of 12 months prior to the moment of observation, with the purpose of living there for a year, at least.

AR=[(P(65, +)/ P(0, 14)]*10^n

P(65, +)=Resident population with 65 and more years old.
P(0, 14)=Resident population aged between 0 and 14 years old.
n=2.