50% seems high to me too if by "family" we mean a group of people living under a single roof. Considering that the average U.S. family unit is now only about four people, that would mean that, on average, one in every eight Americans is a decent guitarist. I don't think so. Maybe one in eight plays some but far less than half of that number are reasonably proficient. (Reasonable proficiency meaning I can stand to listen to them play:-)

Bruce