Cross-sectional average length of life by parity: Example using the US data

High-income countries experienced significant fertility changes since the middle of the 20th century. Traditionally researchers measure the fertility changes by utilising total fertility rate, mean age at childbirth, and parity progression ratio in cohort and period perspectives. However, the cohort and period indexes have a well-known problem; period indexes have a tempo-distortion effect due to use a hypothetical cohort approach, while cohort indexes do not have this effect, but it may provide an outdated picture of current fertility patterns because they are based on information on populations which are no longer at childbearing ages. We introduce alternative way of understanding fertility trends, as the Cross-average length of Life by Parity (CALP). CALP shows the length of time women spent in each parity during the reproductive period and is a period measure including all the cohort fertility information of reproductive age women at a given time. Selecting the US data from Human Fertility Database as an example to demonstrate the measure, we calculate CALP using the hierarchical multistate life table. CALP(2015) shows that women in the US spend 47 % (17.91/38 years) of reproductive years from age 12 to age 50 in childlessness. Then US women spend more years in parity 2 than parity 1 or after parity 3 on average.

Ryohei Mogi is a PhD candidate at CED (Centre d’Estudis Demogràfics), Universitat Autònoma de Barcelona. My substantive research focus is the first childbirth process, especially childless, mate search, and bridal pregnancy (premarital childbearing) comparing Southern European countries and Japan considering historical trends.

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Date & time

Tue 03 Sep 2019, 11.30am–12.30pm


Meeting Room 2, Beryl Rawson Bldg #13, Ellery Circuit, ANU


Ryohei Mogi, Centre for Demographic Studies, Universitat Autònoma de Barcelona


Susan Cowan


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