With all the usual sources of love and security undermined, the horrors of home are simply intolerable and the only alternative is escape.
Again, it takes a while for statistics like this to sink in.
Perhaps it is not so surprising that the fathers escape the blame.
How the girl in question feels about it is, rather cruelly, left unexplored.
Research into what kind of man commits incest has been unable to discover any important differences between them and any other men.
This is arguably the most heartbreaking loss-of-virginity scene in cinema, as a gang of bored Texas teens round up slow-witted Billy and drag him down to the corpulent local hooker to make a man of him.