Sec. 5. (a) The nine (9) classes of the several counties of the state as set out in this chapter are based on a unit factor system. The factors are determined by the relation of the county to the state as established and certified to each county auditor by the state board of accounts not later than July 1 of each year. They are as follows:
(1) Population.
(2) Gross assessed valuation as shown by the last preceding gross assessed valuation as certified by the various counties to the auditor of the state in the calendar year in which the calculation is made.
(b) The factors for each of the nine (9) classes set out in this chapter shall be obtained as follows:
(1) The population of each county shall be divided by the population of the entire state.
(2) The gross assessed valuation of each county shall be divided by the gross assessed valuation of the entire state.
(3) The results obtained under subdivision (1) and (2) shall be added together and the sum obtained for each county shall be divided by two (2).
(4) The result obtained under subdivision (3), multiplied by one hundred (100), determines the classification of each county according to the following schedule: