A unified framework of demographic time

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Demographic thought and practice is largely conditioned by the Lexis diagram, a two-dimensional graphical representation of the identity between age, period, and birth cohort. This relationship does not account for remaining years of life or other related time measures, whose use in demographic research is both underrepresented and incompletely situated. We describe a three-dimensional relationship between six different measures of demographic time: chronological age, time to death, lifespan, time of birth, time of death, and period. We describe four identities among subsets of these six measures, and a full identity that relates the six of them. One of these identities is the age-period-cohort identity, while the other three are relatively novel. We provide a topological overview of the diagrams that pertain to these identities. The 3-d geometric representation of the full six-way identity is proposed as a coordinate system that fully describes temporal variation in demographic data.
Original languageEnglish
Publication date2016
Number of pages25
Publication statusPublished - 2016
EventPopulation Association of America 2016 Annual Meeting - Marriott Wardman Park, Washington, D.C., United States
Duration: 31. Mar 20162. Apr 2016


ConferencePopulation Association of America 2016 Annual Meeting
LocationMarriott Wardman Park
CountryUnited States
CityWashington, D.C.
Internet address


Cite this

Riffe, T., Schöley, J., & Villavicencio, F. (2016). A unified framework of demographic time. Paper presented at Population Association of America 2016 Annual Meeting, Washington, D.C., United States.