By the Numbers - May 7, 2012

That's the percentage of women in the U.S. Air Force -- the highest percentage of female troops of all the armed service branches, according to the Women In Military Service For America Memorial Foundation (PDF), as of September 2011. The Navy is next, at 16.4%. The Marine Corps has the smallest percentage; just 6.8% of Marines are women.

According to the U.S. Department of Veterans Affairs, women are more than twice as likely to develop PTSD than men because, among other things, they are more likely to fall victim to sexual assault. A 2011 news story from the American Association for the Advancement of Science also said women are twice as likely to experience PTSD, but this may have a biological basis. The article discusses a study that "linked a genetic mutation and blood levels of a particular peptide...to the severity of PTSD symptoms in women." While this doesn't have "immediate practical applications," the Emory University psychiatrist and molecular neurobiologist who conducted the study indicated these findings may one day lead to a test that could identify those at greatest risk of developing PTSD.

The VA's National Center for PTSD offers a fact sheet summarizing " research on women's experiences of trauma and PTSD, with a focus on differences between women and men."