  Ever since the studies of Louis-Adolphe Bertillon in the late 19th century it
has been known that marital status and number of children markedly affect death
and suicide rates. This led in 1898 Emile Durkheim to conjecture a connection
between social isolation (especially at family level) and suicide. However,
further progress was long hampered by the limited statistical data available
from death certificates. Recently, it was shown by the present authors that
disability data from census records can be used as a reliable substitute for
mortality data. This opens a new route to investigations of family ties because
census information goes much beyond the limited data reported on death
certificates. It is shown that the disability rate of adults decreases when
they have more family links. More precisely, the reduction of the parents'
disability brought about by the presence of a child reveals that the strength
of ties between parents and child is highest in the first year after birth and
then weakens steadily as the child ages. It will also be seen that the strength
of the bond between husband and wife is highest when they are of same age and
decreases fairly steadily when the age gap increases.

Physics and Society