Revision as of 09:52, 9 January 2010

Age ¹ is another fundamental characteristic of population structure. Generally it is expressed in years, or years and months; in the case of very small children, it may be given in months and days, or in years and decimal fractions of years. Demographers usually truncate the age to the number of complete years ² lived, and this is called age at last birthday ³. Occasionally demographic statistics refer to the age reached during the year ⁴. Where the fraction of the last complete year lived is counted as a whole year, as in some actuarial applications, we speak of age at next birthday ⁵. Stated age ⁶ or reported age ⁶, in a census or vital registration, is often rounded upward to the next integer especially when the next birthday is near. The term exact age ⁷ is used, particularly in life table calculations, to denote the time when an individual reaches his birthday. Census questions include either the date of birth, age at last birthday, or even simply age without further precision. When the knowledge of ages is not widespread, a historical calendar ⁸ may be used to estimate ages. This is a list of events with a known date that occurred during the lifetime of the respondents.

• 2. Thus, age groups (325-2) are usually expressed in completed years and the group aged 6-13 years includes the individuals whose exact ages (322-7) are comprised between 6 and 14 years.

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