Why Does My Auto Insurance Keep Going Up?

For years I've been looking forward to the decline in my auto insurance rates due to my age and great driving record. I really thought that our rates would start to decline. I was totally wrong about that. It seems like every six months when I get my insurance renewal in the mail the premium has gone up again. What's up with that? I'm going to have to start looking around for cheap insurance rates again. It such a pain to start calling insurance companies and getting quotes, but if it saves me a few hundred dollars a year then I it's all worth it.