How do they justify a premium increase of 21.9%

There are so many insurance companies wanting to get business from you and offer you the best rates when you join, but wait until your first premium increase, then they hit you with 21.9%. I do not know how they justify this and in my view this is **************** and *****ing from customers. I have not had one claim in the year, but yet I get these ridiculous increases. I am so fed up of businesses going out to rip you off. Why can they not do business in a civilized, ethical manner. If only my annual salary increase kept up with the insurance companies increases, I wouldn't mind paying their increased premiums, but unfortunately my salary increase is only around 5% per annum. This is not the first company that did this to me. I had the same with Dial Direct. Why do the Insurance companies do this - surely there should be a law against this type of exploitation.