Rates for the classes of insurance to which this chapter applies shall not be excessive, inadequate, or unfairly discriminatory. All rates and all changes and amendments to rates to which this chapter applies for use in this Commonwealth shall consider loss experience and other factors within Virginia if relevant and actuarially sound, provided that other data, including countrywide, regional, or other state data, may be considered where such data is relevant and where a sound actuarial basis exists for considering data other than Virginia-specific data.