This article describes a ratio measure. In the standard operationalization, the numerator of the measure is dependent population (view other ratio measures with this numerator) and the denominator of the measure is population of working age (view other ratio measures with this denominator). The denominator used for reporting is 1. The measurement period is a single point in time.
The numerator counts the total count of some type of entity, and an appropriate convention is set regarding the time within the measurement period that this count is calculated.
The denominator counts the total count of some type of entity, and an appropriate convention is set regarding the time within the measurement period that this count is calculated.
Conceptually, the dependency ratio is an attempt to loosely answer the question: how many non-working (dependent) people need to be supported by a given working person on average? Here, "working" does not necessarily mean somebody employed outside; it also includes people who are engaged in home production. Dependent people may include children and elderly people who are either being taken care of physically or are relying on their savings or pensions to sustain their activities.
The typical operationalization of the dependency ratio is based on age, and this particular operationalization is sometimes called the age-dependency ratio to emphasize the use of age as a proxy for whether somebody is dependent. The age-dependency ratio at a given point in time for a given population is defined as the quotient:
(Number of people in the population who are younger than the lower age threshold or older than the upper age threshold)/(Number of people in the population whose age is between the lower age threshold and upper age threshold)
If we take the lower age threshold and the upper age threshold as 15 and 64 respectively (this means that a person gets to the upper age threshold on his/her 65th birthday), we get:
(Number of people in the population who are younger than 15 or older than 64 -- the latter only includes people who have had their 65th birthday)/(Number of people whose age is in the 15-64 age range -- including people who have had their 64th birthday but not yet had their 65th)