long life made by the Genealogical Record Office of Washington.72 One hundred individuals were picked out at random, each of whom had died at the age of 90 or more, and with the record of each individual were placed those of all his brothers and sisters. Any family was rejected in which there was a record of wholly accidental death (e.g., families of which a member had been killed in the Civil War). The 100 families, or more correctly fraternities or sibships, were classified by the number of children per fraternity, as follows:
| Number of fraternities | Number of children per fraternity | Total number of children in group |
|---|---|---|
| 1 | 2 | 2 |
| 11 | 3 | 33 |
| 8 | 4 | 32 |
| 17 | 5 | 85 |
| 13 | 6 | 78 |
| 14 | 7 | 98 |
| 9 | 8 | 72 |
| 11 | 9 | 99 |
| 10 | 10 | 100 |
| 3 | 11 | 33 |
| 2 | 12 | 24 |
| 1 | 13 | 13 |
| — | — | |
| 100 | 669 |
The average at death of these 669 persons was 64.7 years. The child mortality (first 4 years of life) was 7.5% of the total mortality, 69 families showing no deaths of that kind. The group is as a whole, therefore, long-lived.
The problem