but--here's my for instance:
our daughter stayed home alone at the age of 9 and i was completely comfortable with it. anyone who took any time at all to know her would have known she was perfectly capable of staying by herself.
on the other hand--i would not be comfortable in leaving either of our sons home alone. not now anyways. the oldest is 8 and the younger is 7. neither of them is anywhere near the maturity level that my daughter was at their age.
if you are in doubt or just wondering about it--i would say it is probably best NOT to leave your child home alone as early as 9. it is a lot of responsibility to put on them and if there is an alternative, please, take advantage of it. let kids be kids.
i'm not saying that our daughter is worse off because she stayed by herself at 9--but it did sort of "rob" her of being a true kid. you know?