How do insurers justify car insurance premium increase?

Many of these insurance companies are always ripping you off at every chance they get. I had ONE accident in which the damage was smaller than the deductible, so I for it myself. But when I had to renew my policy, they charged me extra. It's absolutely rediculous. I had to change, luckily, I found this info here: http://www.1stsaveinsuranceinsight.tk and was able to quickly find the lowest rate currently with the same policy. I think I dropped my rate by around $180