61 Pa. Code § 603.1
The aggregate market value approach is commonly termed sales ratio studies. The purpose is to ascertain the average percentage ratios of masses of assessed valuations to masses of bona fide selling prices or properties transferred. These average assessment-sales ratios are then used to convert aggregate assessments into aggregate market values.
The State Tax Equalization Board, in determining the common level ratio, uses a methodology known as the aggregate market value or sales ratio studies approach. In re Armco, Inc., 515 A.2d 326 (Pa. Cmwlth. 1986); appeal denied 533 A.2d 714 (Pa. 1987).