The origin of a chart indicating the likelihood of conception linearly declining with age

- a literature survey
TANAKA Sigeto <>
(Graduate School of Arts and Letters, Tohoku University)
Unpublished manuscript (2017-06-12)

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OSF project: {DOI:10.17605/OSF.IO/7TKND}


BACKGROUND: A chart indicating the likelihood of conception linearly declining with age (86% for women aged 20-24, 78% for 25-29, 63% for 30-34, 52% for 35-39, 36% for 40-44, 5% for 45-49, and 0% for 50 and over) is widely used on Internet fertility sites and by medical professionals. Its origin has been unknown until now.
OBJECTIVE: To explore the origin of the chart.
METHODS: A literature survey.
RESULTS: Among the seven points on the curve, three are based on data that are not the likelihood of conception, while four are probably derived from oversimplified description of fecundability estimates for Hutterite and Taiwanese women in the 1950s and 1960s. Two professionals contributed to the making of these data.
CONCLUSIONS: The chart was fabricated and exaggerates the effect of age on the likelihood of conception. At least two professionals are responsible for the fabrication.
CONTRIBUTION: This paper describes a case of misinformation about demographers' research results. It issues a warning against misuse of demographic knowledge in medical, commercial, educational, and political contexts.


fecundability, natural fertility, popular science, misinformation, research ethics, fabrication, obstetrics, gynecology, reproductive medicine, demography


  1. The Chart in Question
  2. Tracing the Origin
  3. Read the Figures as Fecundability
  4. Evaluation

Tables and Figures


  1. BabyCenter, 2007, "Chart: The effect of age on fertility," (Retrieved {})
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  3. Bendel, J. P., 1978, "A model of births for developing countries and its use in the study of demographic effect of birth control" (PhD thesis), Pittsburgh: Carnegie-Mellon University. (UMI Dissertation Services; 7814379) {NCID:BA8994655X}
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  27. Tanaka S., forthcoming, "Another science war: Fictitious evidence on women's fertility and the 'egg aging' panic in 2010s Japan," Advances in Gender Research, 24. {}
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Findings in this article were partly presented at a symposium on academic ethics held by an activist network (November 30, 2015 in Tokyo), at a symposium held by the Science Council of Japan (June 18, 2016 in Tokyo), and at the 26th annual conference of the Japan Society of Family Sociology (September 11, 2016 in Tokyo). The author thanks to comments from the participants (additional information is on The author also thanks Editage ( for English language editing.


Questions/comments are welcome.

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