親と子の各同胞における性比並びに出生順位の差異に関する研究

概要

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The sex ratio and birth order between siblings of parents and their children were surveyed on 4, 700 families of students who were attending 6 public junior high schools in the suburbs of a large city.Results obtained are as follows:(1) The sex ratios in the siblings of parents and their children were 103 and 97 respectively.(2) The mean number of the siblings of the children was 2.7 and that of parents was as high as 5.1.(3) When siblings were two in number, cases where both siblings were males appeared more frequently among the children than the parents, and vice versa in the case where both were females. This phenomenon appears to be characteristic of recent Japan.(4) When siblings were more than four, the birth order among males and females corresponded to the theory of“random walk”in case of the parents, but not so in the case of children.These results seem to imply that recent changes in socio-economic status as well as propagation of family planning have bearing on sex ratio and birth order.