THeory (Actually it was the explanation an insurance agent gave me years ago)
There are really not all that many Insurance companies. What happens is a company Sells you a policy and then THEY sell it to a "Re-INsurer" and there are only so many of those.. A few companies (IE: AAA-Michigan) carry their own and do not resell (Got this from an AAA agent).
So when the SHTF something like 9-11 or a Hurricane or Tornados or other natural disaster or some other major disaster like what is it now 19 School shootings so far this year... The big Re-Insurance companies take a MAJOR hit. So in order to remain profitable, and if possible Even more so they reaise the rates they charge to your smaller insurance underwriter.
Not all Underwriters (IE: Progressive, GICO, Nationwide, Allstate) re-sell to the same Re-Insureres so some will have better rates than others.
Now that's the official statement of my old AAA agent.. I'm no longer with them.
My theory: Raising rates is the insurance company's way of promoting a Song from, I believe the 50's
Shop Around. by the Miracles.
My Mamma Told me.. To do The Shop Around.