An Act amending the act of June 27, 1939 (P.L.1199, No.404), entitled "An act relating to the assessment of real and personal property and other subjects of taxation in counties of the first class; providing for the appointment of members of the board of revision of taxes by the judges of the courts of common pleas; providing for the appointment, by the board, of personal property assessors, real estate assessors and assistant real estate assessors, clerks and other employees; fixing the salaries of members of the board, assessors and assistant assessors, and providing for the payment of salaries and expenses from the county treasury; prescribing the powers and duties of the board and of the assessors, the time and manner of making assessments, of the revision and notice of assessments and of appeals therefrom; prescribing the records of assessments; and repealing existing laws," providing for the definition of "assessment ratio"; and establishing a revenue-neutral tax rate after a countywide revision of real property assessment.