The PSM evaluates whether the allocation of the combined operating profit or loss earned by one or more controlled transactions is arm's length by reference to the relative value of each controlled taxpayer's contribution to that combined operating profit or loss. The relative value of each controlled taxpayer's contribution to the success of the relevant business activity must be determined in a manner that reflects the functions performed, risks assumed, and resources employed by each participant in the relevant business activity. In general, three forms of the PSM are specified: (i) the comparable profit split method (“comparable PSM”), (ii) the contribution profit split method (“contribution PSM”) and (iii) the residual profit split method (“residual PSM”).