(a) As used in this Code section, the term "population" means population as determined by the United States decennial census of 1970 or any future such census.

(b) The proceeds of the local income tax collected by the commissioner pursuant to this article shall be disbursed as soon as practicable after collection as follows:

(1) One percent of the amount collected shall be paid into the general fund of the state in order to defray the costs of administration;

(2) Except for the percentage provided for in paragraph (1) of this subsection, the county levying the tax shall receive that proportion of the proceeds of the tax which the population of the county in the area outside the limits of any municipality in the county bears to the total population of the county; and

(3) Except for the percentage provided for in paragraph (1) of this subsection, each incorporated municipality lying wholly or partially within the county levying the tax shall receive that proportion of the proceeds of the tax which the municipality's population lying wholly within the county levying the tax bears to the total population of the county.