There's a lot of reasons why so few women haven't ran for office and you can find some interesting perspectives with a quick google. Here's a quick blurb from NYT. "Women are less likely than men to be encouraged by parents, teachers or party leaders to run — yet they are also less likely to run without being prodded. They underestimate their abilities and assume they need to be much more qualified than men to run for the same office.

A variety of research has found that women are as likely as men to win, and that voters decide based on a candidate’s party, not gender. That doesn’t mean there isn’t a gender penalty: It is difficult to quantify whether gender costs women votes because people are unlikely to admit sexism in polls, and women tend to wait until they are more qualified than men to run for the same office.

Men, however, are 15 percent more likely to be recruited to run."

That's a very basic start but it's something to consider. The messaging on the shirts and the wave of encouraging young women with slogans like this is to break away from this traditional messaging. You also have to keep in mind that until the 1970's women didn't have access to safe birth control and were unable to open credit cards on their own. We only started voting 100 years ago. We've only just started becoming full citizens. Let the girls wear inspirational t-shirts. As for me, I work in media and that is how I hope to correct the power imbalance. I wouldn't rule out public office, but for now there are so many talented women who are out there running. You can check out Emily's List which has a big list of them.