Investigations on the changes of sex ratio in Germany from 1826 up to 1978.

The changes of the secondary sex ratio in Bremen (North Germany) from 1826 up to 1978 are compared with those of Germany in the period from 1872 to 1978. To some extent there are marked differences. The oscillation of the secondary sex ratio in Bremen is more extended in Germany. On the average in Bremen the values are lower in the 19th century than in the 20th. For Germany higher values are observed in the years between 1915 and 1959. The changes of reproductive performance, indicated by birth rate. Supposing that the primary sex ratio is dependent on the time of insemination within the intermenstruum, the same figures of monthly distribution of secondary sex ratio and birth frequency can be expected. In fact, the seasonal variations proved to be not significant and do not show the expected parallel figures.