The Dangers of Drawing Cohort Profiles From Period Data: A Research Note

• DOI: 10.1215/00703370-11067917
• Publication Date: 2023-11-15T10:52:38Z
• Authors: Alyson A. van Raalte; Ugofilippo Basellini; Carlo Giovanni Ca...; Marília R. Nepomu...; Mikko Myrskylä
• Keywords: Cohort effect

Abstract Drawing cohort profiles and forecasts from grids of age–period data is common practice in demography. In this research note, we (1) show how demographic measures artificially fluctuate when calculated the diagonals rates because timing cohort-size bias, (2) estimate magnitude these biases, (3) illustrate prediction intervals for indicators mortality may become implausible drawn Lee–Carter methods grids. These biases are surprisingly large, even created single-age, single-year period data. The danger that overinterpret deviations expected trends were induced by our own manipulation.