Age is usually determined in completed years as of the time of enumeration from replies to a question on month and year of birth. (Only year of birth by quarter is actually carried on census basic records.) Age is estimated from other information reported in the schedule if the respondent fails to indicate birth date. Age is tabulated by single years from under 1 year, 1, 2, 3, . . . to 98, 99, and 100 years or more; and by many different age groupings, such as five-year age groups. Median age is calculated as the value which divides the age distribution into two equal parts, one-half the cases falling below this value, one-half above. Median age is generally computed from the age intervals or groupings shown in the particular tabulations, except that median age in tabulations of single years of age is based on five-year age groups.