[Report 1899] / Medical Officer of Health, Leeds City.

  • Leeds City Council
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: [Report 1899] / Medical Officer of Health, Leeds City. Source: Wellcome Collection.

    114/182 (page 104)
    the number of houses in each intercept counted for 1898, we increased or decreased the census population of the intercept at the same rate at which the houses had increased or decreased. When these fictitious populations were added together the result was in excess of the Registrar General s population for the year. Up to this point the method was to all intents and purposes the same as last year’s. Instead, however, of diminishing the fictitious populations for 1898 proportionately to their amounts, we have in each case substracted the census population from the fictitious population, and increased 01 diminished the latter proportionately to these differences. The results vary very little, so iar as 1898 is concerned, from those given last year, but in dealing with 1899 the difference is considerable. Using these differences between the census and the “fictitious” populations, we have increased or diminished the newly accepted populations lor 1898 again proportionate!} to these differences, but so as to make the total correspond with the population for 1899,* accepted by the Registrar General. In the same way the populations for 1892 and 1897, used in the decade tables for phthisis and diarrhoea, have been obtained. * Suppose the census population of the city to he P, and to be made up of the intercept populations A + B + C + D + &c , = P. Suppose the population for 1898 to have increased to P2 by geometrical progression, and what is called above the “fictitious” populations of intercepts, to amount also on geometrical progression, from ratios of increase in dwelling-houses to A„, B.2, C2, D2, &c., the sum of the latter amounting to S. If S = P2 no correction is of course required. If not (and as a rule in Leeds'S exceeds P2), then subtract P2 from S, and call the difference Q. In the same way subtract the census from the “ fictitious ” population of each intercept, and let the differences be a, b,-c, d, &c. Adding these differences (algebraically), use their sum as divisor of the difference, thus: Q A (a + b - c + d + &c.) The quotient is now multiplied by a, b, -c, d, &c., separately, and the product of each operation is the correction for the fictitious intercept population, and has to be subtracted from it. It will be noticed that one of the intercept differences, C2-C, is supposed to qe _ c. That is, the population of the intercept was decreasing. Subtracting the correction - c from C2 is really adding it. In obtaining the 1899 intercept popula¬ tions from those for 1898, the increase of the whole city between 1898 and 1899 was divided by (a + b - c + d + &c.), and the quotient multiplied by a, b, - c, d, Ac. The results were then added to the corrected intercept populations for 1898, observing of course the algebraic signs. The populations for 1892 and 1897 used in the decade tables were obtained similarly.