The spacing of births in the families of university graduates.

In 944 completed families of Cornell University graduates of the classes of 1919, 1920, and 1921, first births occur about 2.5-2.9 years after marriage. The intervals between successive births ar usually longer than the interval between marriage and the first birth. In families of a given size the average length of the interval increases for each successive birth, the first birth coming after the shortest time interval and the last usually after the largest. Inquiry is being made to discover whether this spacing pattern is social or biological.