i happened to find the book with all the italian inbreeding
data“Consanguinity, inbreeding, and genetic drift in Italy” by
cavalli-sforza, et. al. — on google books.  and i found
something real interesting in it!  remember how i was wondering
what the inbreeding numbers for italy were before 1910? well,
cavalli-sforza, et. al., have data stretching back to 1780
(cool!) and this is what they look like (the solid line):
before i go any further, this chart doesn’t represent the actual
numbers (no label on the y-axis, see?). instead, it’s a model to
(as the caption reads): “explain the peculiar trend of
consanguinity in italy.” that peculiar trend was low
consanguinity at the start of the period (1780); then rising, at
first gradually, but then with increasing speed until hitting a
peak around the end of wwi; and then a falling off again.  the
authors write [pg. 240]:  “Figure 9.13 is an attempt at a
simple, semiquantitative explanation of the whole process. The
curves assumed to generate the phenomenon are two