The Social Direction of Evolution: An Outline of the Science of Eugenics — A Closer Reading

London were canvassed on these bases, which are certainly significant, though not infallible, indices to the character of a community. His results are shown in the briefest possible form in Table III.

_Correlation of the Birth Rate with Social and Physical Characters of London Population._ (From Heron.)

CORRELATION COEFFICIENT. With number of males engaged in professions -.78 With female domestics per 100 females -.80 With female domestics per 100 families -.76 With general laborers per 1,000 males +.52 With pawnbrokers and general dealers per 1,000 males +.62 With children employed, ages 10 to 14 +.66 With persons living more than two in a room +.70 With infants under one year dying per 1,000 births +.50 With deaths from pulmonary tuberculosis per 100,000 inhabitants +.59 With total number of paupers per 1,000 inhabitants +.20 With number of lunatic paupers per 1,000 inhabitants +.34

This table gives the results of the calculation of coefficients of correlation between the birth rates and the conditions enumerated. We may just recall that this coefficient is a measure of the regularity with which the changes in two varying conditions or phenomena are associated: and further that a coefficient of 1.0 indicates perfectly regular association, 0.75 a very high degree of regularity. The first line of the table then, for example, means that when these twenty-seven districts were sorted out, first, with reference to the number of professional men dwelling in them, and then with reference to their respective birth rates, there was found a very high degree of regularity (coefficient of correlation = -.78) in the association of these two conditions--birth rate and number of professional men. Here is a very close relation, _but_, the sign of the coefficient is _negative_. The significance of this negative sign is that among the communities studied those where the number of professional men is the larger show always, at the same time, the lower birth rates. Coming to the second line of the table, it seems fair to assume that the number of servants employed in a district in proportion to the total number of residents or families there, gives a fairly though not wholly satisfactory indication of the social character of the community. Measurement of the actual relation between the proportional number of servants employed in a community and the birth rate in that community, gave practically the same result as in the case of the number of professional men. The more servants employed in a district the lower its birth rate. Two methods of measuring this relation gave essentially the same result; comparison of the birth rate with the ratio of domestics, first to the number of families, second to the number of females, gave -.76 and -.80 respectively--very high coefficients and both negative.

But the sign changes and becomes positive when we come to other comparisons. When we count the relative number of pawnbrokers and general dealers, of "general laborers" (that is, men without a trade and without regularity of occupation and employment), of employed children between the ages of ten and fourteen, of persons living more than two in a room, when we consider the infant death rate, the death rate from pulmonary tuberculosis, and the relative number of paupers,--then we find the signs of the coefficients are all positive, and on the average the coefficients are more than 0.50--a moderate to high degree of regularity of the relation. The districts characterized by the larger numbers of such individuals or by higher death rates of these kinds, are at the same time the districts where the birth rates are the higher.