In Brodie v. Workers' Comp. Appeals Bd. (2007) 40 Cal.4th 1313, the Supreme Court considered the impact of Senate Bill No. 899 on the following question: "When a worker suffers an industrial injury that results in permanent disability, how should the compensation owed based on the current level of permanent disability be discounted for either previous industrial injury or nonindustrial disabilities?" (Brodie, at p. 1317.) In Brodie, the permanent disability level for each injured worker could be partially attributed to either (a) a prior industrial injury that had resulted in a prior permanent disability award; or (b) nonindustrial causes. (Brodie, supra, 40 Cal.4th at pp. 1318-1319.) In Brodie, no one argued, as Permanente does here, that apportionment was required when multiple industrial injuries had been suffered but no permanent disability previously awarded. (Ibid.) The Brodie court attributed the 2004 statutory revisions to the following goals: (1) reversal of the rule barring apportionment "if the disability arose in part from an interaction between an industrial cause and a nonindustrial cause, but the nonindustrial cause would not alone have given rise to a disability"; (2) reversal of the rule allowing "employees wide latitude to disprove apportionment based on prior permanent disability awards by demonstrating that they had substantially rehabilitated the injury." (Brodie, supra, 40 Cal.4th at pp. 1326-1327.) The Brodie court reasoned that former sections 4663 and 4750, "as interpreted by the courts, were inconsistent with the new regime of apportionment based on causation, as well as the conclusive presumption that previous permanent disability still existed for apportionment purposes. ( 4663, subd. (a), 4664, subds. (a), (b).) Former section 4750 required consideration of the new injury 'by itself and not in conjunction with or in relation to the previous disability or impairment' and further called for compensation for the later injury to be determined 'as though no prior disability or impairment had existed.' But under Senate Bill No. 899 ... , the new approach to apportionment is to look at the current disability and parcel out its causative sources--nonindustrial, prior industrial, current industrial--and decide the amount directly caused by the current industrial source. This approach requires thorough consideration of past injuries, not disregard of them. Thus, repeal of section 4750 was necessary to effect the Legislature's purposes in adopting a causation regime." (Brodie, supra, 40 Cal.4th at pp. 1327-1328.) The court observed: " 'we do not presume that the Legislature intends ... to overthrow long-established principles of law unless such intention is clearly expressed or necessarily implied.'" (Brodie, supra, 40 Cal.4th at p. 1325.) Given that the legislative goals just noted sufficiently explained the reforms, the absence of legislative history regarding calculation, and that the plain language of the new statutes did not compel any particular method of calculation, the Supreme Court held that Senate Bill No. 899 had not superseded Fuentes. (Brodie, supra, 40 Cal.4th at pp. 1325-1332.) In Brodie, the Supreme Court concluded, "nothing in current section 4663 or section 4664 expressly requires formulas A, B, C, modified C, or any other approach to calculating compensation. Nor does anything in the language implicitly do so." (Brodie, supra, 40 Cal.4th at p. 1325.) With respect to apportionment, however, we agree with the Board that "the Legislature has not been silent." As amicus curiae CWCI contends: "The permanent and stationary date of successive injuries is now irrelevant, because the requirement of a preexisting disability to support apportionment no longer exists." The Legislature rejected the combination of distinct industrial injuries when it repealed former section 4750 and enacted sections 4663 and 4664. Accordingly, any presumption in favor of the continued validity of Wilkinson does not apply. (Brodie, supra, 40 Cal.4th at p. 1325.)