On or before July 1, 1996, the rating organization licensed pursuant to § 38a-672 shall file with the Insurance Commissioner a method of computing workers’ compensation premiums which does not discriminate against or penalize employers in the construction industry solely because they pay higher wages than other employers to workers in the same job classification. Such method shall grant premium credits to construction contractors (1) who have workers’ compensation insurance policies in which at least fifty per cent of the premium is attributable to construction classifications and (2) whose experience modification is unity or less as of July 1, 1996. Such credits shall apply to workers’ compensation insurance policies issued or renewed on or after July 1, 1996.