When people do not know exactly how old someone is, they often guess ages that end in preferred digits, such as 0 or 5. Demographers refer to this as “age heaping.” One approach for measuring age heaping in population data is called “Whipple’s Index.” Learn more about age heaping and Whipple’s index in our blog, Age Heaping in the 2020 Census Demographic and Housing Characteristics File (DHC).