What type of rating is used for companies with high credibility in their insurance history?

The option referring to experienced rating is correct because this type of rating system is specifically designed for companies that have a considerable amount of historical data demonstrating their claims experience. In accident and sickness insurance, an experienced rating allows an insurer to adjust premiums based on the actual loss experience of the policyholder, reflecting the credibility of their historical claims data.

Companies with high credibility typically have a significant volume of business, which provides a more reliable basis for estimating future claims cost based on past performance. This data allows insurers to have confidence in adjusting the rates more accurately according to the specific risk profile of the company.

The other rating types do not align with the characteristics of companies with high credibility. A blended rating combines elements of different rating methods but doesn’t specifically reflect a company's historical performance as accurately as experienced rating. Manual rating relies on predetermined rates and classifications without adjusting for an individual company's experience. An unrated classification indicates a lack of available rating data, which is opposite of what is being assessed in terms of high credibility in insurance history.