The department shall make sales ratio studies in all counties of the State and when, in the judgment of the department, a county needs to reassess or remap property, the department shall make application to the circuit court in which the county is located for a determination of whether or not the county shall be required to commence reassessment or remapping. If the circuit court determines that the county needs reassessment or remapping, such county shall be required to commence the reassessment or remapping within thirty days of such determination.