When is the best time to pickup?

Well according to this graph, girls should have the best chances to pickup guys in their early 30's while for guys it's all gravy all the way up to the 50's. This is supposedly based on US census information, except it doesn't add up... How can there be so much more single girls then guys? I mean, I understand the lines should taper off at different rates because of life expectancy. But I don't see why the area under the curve should be so different.. unless man are marrying each other?