I don't agree. I think that single people may believe that they are happier and believe that they are living a more authentic life, except for most single people, they haven't experienced a real relationship before. An individual may feel more "free" or "independent" being single, but coming from experience, once you have found the right person to be in an romantic relationship with, you start to feel something different. I wouldn't disagree that single people are happy, they do have freedom and essentially less responsibility. However, I believe that being in a relationship and having someone that you can share everything with and be your true self around, brings someone a different kind of happiness. In many ways, a better happiness.