Although it is illegal to not hire a woman because she's married, firms often get away from doing so. The law makes things worse since firms can not discuss family plans, or negotiate lower pay in exchange for maternity leave or more flexable hours.

http://content.time.com/tim…

Actually a lot since it means that employing women of the age that families begin is more expensive.

If you factor out personal descisions it's 98 cents.

Childless women under 30 earn more than men on average.