For the US, 1850, men outnumbered women by about 3% in 1850; women outnumbered men by 4% in 1970.  An article in the March 20, 2000 issue of Forbes discusses the question of gender ratios, in a report on a recent book which apparently makes the same argument I offer in the text. I plan to add a link to the article when it becomes available online.

Shoshonna Grossbard-Shechtman at San Diego State has done work in the area, including looking at sex ratios. She published a book a few years ago called The Economics of Marriage, but I have not yet had a chance to look at it.