Actually I remember reading [1] that since the recent economic downturn, because it affected men much more than women, more women are marrying "down" than are marrying "up".

I agree that our societal norms haven't caught up with the fact that there are no longer enough high status men and low status women for all the women to marry up anymore, so the social pressure is still there but it seems to be changing fairly quickly.

[1] http://www.guardian.co.uk/society/2012/apr/08/marriage-and-c...