For the calendar year 1984 and each calendar year thereafter, each employer shall pay contributions at a percentage rate equal to the greatest of 2.7%, or 2.7% multiplied by the current adjusted State experience factor, as determined for each calendar year by the Director in accordance with the provisions of Sections 1504 and 1505, or the average contribution rate for his major classification in the Standard Industrial Code, or another classification sanctioned by the United States Department of Labor and prescribed by the Director by rule, with respect to wages for insured work paid during such year. The Director of Employment Security shall determine for calendar year 1984 and each calendar year thereafter by a method pursuant to adopted rules each individual employer's industrial code and the average contribution rate for each major classification in the Standard Industrial Code, or each other classification sanctioned by the United States Department of Labor and prescribed by the Director by rule. Notwithstanding the preceding provisions of this paragraph, the contribution rate for calendar years 1984, 1985 and 1986 of each employer who has incurred liability for the payment of contributions within each of the two calendar years immediately preceding the calendar year for which a rate is being determined, and the contribution rate for calendar year 1987 and each calendar year thereafter of each employer who has incurred liability for the payment of contributions within each of the three calendar years immediately preceding the calendar year for which a rate is being determined shall be determined as provided in Sections 1501 to 1507.1 , inclusive. Provided, however, that the contribution rate for calendar years 1989 and 1990 of each employer who has had experience with the risk of unemployment for at least 13 consecutive months ending June 30 of the preceding calendar year shall be a rate determined in accordance with this Section or a rate determined as if it had been calculated in accordance with Sections 1501 through 1507, inclusive, whichever is greater, except that for purposes of calculating the benefit wage ratio as provided in Section 1503, such benefit wage ratio shall be a percentage equal to the total of benefit wages for the 12 consecutive calendar month period ending on the above preceding June 30, divided by the total wages for insured work subject to the payment of contributions under Sections 234, 235 and 245 for the same period and provided, further, however, that the contribution rate for calendar year 1991 and for each calendar year thereafter of each employer who has had experience with the risk of unemployment for at least 13 consecutive months ending June 30 of the preceding calendar year shall be a rate determined in accordance with this Section or a rate determined as if it had been calculated in accordance with Sections 1501 through 1507.1 , inclusive, whichever is greater, except that for purposes of calculating the benefit ratio as provided in Section 1503.1, such benefit ratio shall be a percentage equal to the total of benefit charges for the 12 consecutive calendar month period ending on the above preceding June 30, multiplied by the benefit conversion factor applicable to such year, divided by the total wages for insured work subject to the payment of contributions under Sections 234, 235 and 245 for the same period.
820 ILCS 405/1500