Good article on what type of demographics click on natural vs. paid listings.

Is Your Search Marketing Campaign Lopsided?:

Women find paid search advertisements more relevant than men. Of female respondents, 43.1 percent choose a paid search advertisement, where just 34.6 percent of men click on a search ad when asked to choose the most relevant search result to a sample query.

If your products or services target a female demographic and the majority of your traffic and conversions come from 'natural' search results, you may miss a significant opportunity by failing to buy search ads. According to Jupiter Research, site categories most visited by women include personal care, cosmetics, home fashion and toys.

Marketers competing in these online markets would be wise to begin testing a paid search advertising program and devoting more resources to Overture and Google AdWords campaigns to attract some of that missed audience."