A birth cohort is a group of individuals born during a given calendar time period within a specified geographical region. For example, the U.S. 1950 annual birth cohort refers to the group of people born in the United States during the calendar year 1950, and the 1950 to 1952 birth cohort identifies those born during the period covering the three consecutive calendar years 1950, 1951, and 1952. Birth cohort analysis is an observational cohort analysis (as opposed to an experimental cohort analysis such as clinical trials) of an entire birth cohort or of a selected sample of the birth cohort.

Data for birth cohort analysis are best depicted by a Lexis diagram with the horizontal axis denoting calendar time and the vertical axis denoting age wherein ...