Today’s US woman is expanding her “sphere of influence,” according to September 2011 research from Fleishman-Hillard, Hearst and Ipsos Mendelsohn. Through social networks and web tools, she is both contributing and seeking out purchase recommendations from friends and followers.According to the survey, 54% of US female internet users said they feel a responsibility to help friends and family make wise purchase decisions, and nearly half said they influence friends and family to buy—or not buy—a product or service on a regular basis. When a similar study was conducted in September 2008, only 31% of women said they felt they regularly influenced other people’s purchase decisions.

Social networks and social reviews have played an important role in this rise in purchase influence. In the last six months, 46% women said they had read reviews about a product on a website. Moreover, 33% had recommended a specific product or service to someone, and 30% had reviewed a product or service on a website.

Women’s use of social networks such as Facebook continues to grow year over year—73% of US female internet users now use Facebook, compared with 65% in 2010. The number of Facebook friends for the average US woman also continues to grow, and so does the number of brands she follows. According to the Fleishman-Hillard/Hearst study, women follow 12% more brands than they did in 2010.

In terms of talking about brands and making product recommendations on social networks, millennials appear to be standouts. Nearly half of online millennial women said they prefer shopping on the internet vs. in a store. And 51% use social networks to share commentary related to products and shopping.

Research from JWT Intelligence, the data arm of marketing communications company JWT, further demonstrates millennials’ aptitude for shopping-related social media activities. As of June 2011, 63% of millennial internet users had asked for opinions on products on Facebook, 60% had purchased a product based on a social recommendation and 57% had posted a status update about a product.

When breaking it down by gender, about one-third of all female respondents said they had used Facebook for the aforementioned activities.

Marketers should embrace demographic distinctions—for both gender and age—to reach influencers and showcase their brands in the best light. Not only are women more active now on social sites, but their likelihood to recommend and act on recommendations is growing.

Even marketers who target demographics other than women should keep the female influencer in mind when developing campaigns and social media programs.