I think middle class is a better indicator. It shows that if a man dedicates himself to his work, he can prosper, which shows the level to which society is free. Don't get me wrong, how the society treats its workers and its poor is vital, but the common man doesn't have use for the ammenities required to make a middle class person, so you're missing out on a lot of details.

It could also be argued that your working women won't give you a good idea of the opportunities provided to the fairer sex.