Whipple's index

Whipple's index (or index of concentration), invented by American demographer George Chandler Whipple (1866–1924), is a method to measure the tendency for individuals to inaccurately report their actual age or date of birth. Respondents to a census or other survey sometimes report their age or date of birth as a round number (typically ending in 0 and 5), or to be more culturally favorable, for example, so that they appear younger or to have been born on a date considered luckier than their actual date of birth. The process of reporting a rounded or “lucky” age is known as age-heaping. Calculation The index score is obtained by summing the number of persons in the age range 23 and 62 inclusive, who report ages ending in 0 and 5, dividing that sum by the total population between ages 23 and 62 years inclusive, and multiplying the result by 5. Restated as a percentage, index scores range between 100 (no preference for ages ending in 0 and 5) and 500 (all people reporting ages ending in 0 and 5). The UN recommends a standard for measuring the age heaping using Whipple's Index as follows: Applicability Although Whipple's index has been widely applied to test for age heaping, it assumes that the heaping is most likely to occur in 5 and 10 year intervals or some other fixed interval based on digit preference or rounding. While other measures of age heaping, such as Myers' Blended Index, can be applied to find preferences for any terminal digit, the patterns of heaping may be complex.