PHOENIX – Last year only 21 percent of those ages 18-34 in Arizona signed up for health insurance, making this one of the lowest states in the country for enrollment in that age group. The Arizona Public Interest Research Group is looking into why young adults are so reticent to sign up. One reason is the belief among young adults that they are not very susceptible to getting hurt or sick. The group is trying to educate these so-called “invincible” young adults about the benefits of having health insurance.