1. See Calot, Gérard, L’observation de la féconditéà court et moyen terme; Population, 36, 1981, 1. — pp. 9–40;
2. see also Höhn, Charlotte, Die CALOT-Methode zur aktuellen Beurteilung von Geburtenniveau und -trend; Zeitschrift für Bevölkerungswissenschaft 7, 1981, 2. — pp. 231–254.
3. Since 1980 (Höhn) resp. 1982 (Linke) Bundesinstitut für Bevölkerungsforschung, Wiesbaden.
4. The mean is derived from age-specific fertility rates and not from absolute numbers of births by age of mother. This also applies to the standard deviation.
5. It appears from survey data that childlessness has decreased in France from birth-cohort 1931 (12.4% of childless women) to birth-cohort 1945 (8.0%) and then increased (9.7% in birth-cohort 1950 and possibly 11% in birth-cohort 1955). The surprising point is not so much this recent increase but rather the very low proportion in the 1945 birth-cohort.