I don't know, I just tend to think that doctors are getting better at diagnosing bipolar, especially in people with BP 2. Even I was misdiagnosed for years with depression, and when I got my BP NOS diagnosis I was both shocked and relieved. Now I knew what monster I was dealing with. I have since gone on to be diagnosed with BP 1 several times because my symptoms changed and became more severe, but I'm glad it's settled. I was in limbo for far too long.