The Demographic evolution of human populations / edited by R.H. Ward and K.M. Weiss.

Date:
1976
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The Demographic evolution of human populations / edited by R.H. Ward and K.M. Weiss. Source: Wellcome Collection.

    24/174 page 10
    10 R. H. WARD AND К. M. WEISS fertility, и f., by age x, the values being 0*05, 0*23, 0*45, 0*65, 0'83, 0-95, 1-0 for the 7 age classes in the reproductive period (Henneberg, this volume). This similarity in age patterns of relative fertility has been noted by Talwar (1970) and also by Weiss (1973a,6) who used this fact to construct model life tables and indices of growth regulation. Using these values Henneberg calculates the reproduction actually achieved compared to that which would have obtained had there been no mortality in the reproductive period. The Net Reproductive Rate {R^, representing the number of females produced per female born, is computed from the rate of juvenile mortality and presumed sex ratio at birth while a range of values is given for children born to women reaching menopause, С/д (equivalent to the Total Fertility Rate or TFR). Finally a Biological State Index (/j,,) is derived to reflect the amount of reproductive potential lost as a consequence of mortality before and during the reproductive period. This index can be construed as indicating the opportimity for selection to act through mortality differentials as perceived from skeletal data (in which we are restricted to an analysis of mortality only). Further, the total index, Jj,, is a function of juvenile mortality (indicated by sxirvivorship to age 15) and mortaHty during the reproductive period (indicated by viz: /j, = (see below). The relationship between the various indices constructed by Henneberg is indicated by defining them in terms of age-specific birth and death rates. First we note that Ug (or completed family size) is equivalent to the Total Fertility Rate (TFR) or sum of age-specific birth rates, b^, i.e. TFR = У b^. Similarly the archetype of fertility, 1 — s^,, represents the proportion of the Total Fertility Rate achieved by age x, i.e. 1 - -y« = 2 ^i/ 2 (^) i=15 »=15 Further, since the proportion of individuals who die at age x in the reproductive period, <4, can be written in terms of survivorship to age x, 4, i.e. / ] <o ^ 4 = 24 = 1 ¿15 a!=15 ,. : we may derive as follows: f,!;«iif.; ®=15 ^ WH - -4. (from Henneberg—3), and substituting for d^, and 1 — svre. have: ^x ^arfl I V = I I M ^ I b- C7) \ Ф « . /it¬ 's * 2 ^ ^+1 ' 2 .. Л . X I h »ШШЙ» ï/'Q')
    digitised image 1
    digitised image 2
    digitised image 3