The ratio of the number of people in non-working age to the number of people in working age.

As a non-working age most commonly is defined as the age 0-17 (pre-working age) and 60 years and more for females and 65 years and more for males (post-working age); working age refers to 18-59/64 years (18-59 for females and 18-64 for males).
Other non-working age grouping is 0-14 years and 65 years and more; working-age is 15-64 years - for males and females.