Brodie v. Workers' Comp. Appeals Bd. (2007) 40 Cal.4th 1313 considered the question: In what manner should compensation for a current level of permanent disability (PD) be reduced when payments have been made for a previous industrial injury? (Brodie, supra, 40 Cal.4th at pp. 1317, 1320; Sen. Bill No. 899 (2003-2004 Reg. Sess.).) Before Brodie, there was a split of authority among the Courts of Appeal. (Brodie, supra, at pp. 1318-1319.) The Brodie court concluded that the formula used in Fuentes v. Workers' Comp. Appeals Bd. (1976) 16 Cal.3d 1, still applies to apportioning compensation of PD. (Brodie, supra, at p. 1317.) The Fuentes formula ensures that employers are liable only for that portion of the worker's PD attributable to the current industrial injury. (Brodie, supra, at p. 1321.) As the Brodie court explained, PD payments are calculated by expressing their degree as a percentage and then converting that percentage to an award based on a disability payment table. (See Brodie, supra, 40 Cal.4th at p. 1320.) Until April 1972, the table was straightforward and linear. A worker would receive four weeks disability for every percentage point of disability. (Id., at pp. 1320-1321.) Thus, if a worker sustained 10 points of disability, he or she would receive 40 weeks of disability payments. If a worker sustained 90 points of disability, he or she would get 360 weeks of such payments. If a worker previously suffered 10 points of disability, and later sustains another injury which results in a total PD rating of 90 percent (i.e., the new injury contributes another 80 percent to the PD), the employer would only be responsible to pay for the difference between the new 90 percent rating and the old 10 percent rating, or 80 percent. Under the old table, it would not matter whether one calculated the amount based on the difference in percentages or the difference in the dollar amount it represented. But, in 1971, the Legislature amended the law to create a sliding scale of benefits that more generously compensated workers who sustained more severe disabilities. (Brodie, supra, 40 Cal.4th at p. 1321.) Under the new table, one would arrive at different amounts an employer owed for successive injuries depending on whether one used the percentage difference between the disabilities caused by each or the dollar amount they represented. That is because the table was no longer linear, but deviated upwards depending on the severity of PD. (Id., at pp. 1321-1322.) The amount of money a worker would receive depended on whether one subtracted the percentage difference between the two PD awards and consulted the table, or subtracted the dollar amount of the old rating from the dollar amount of the new rating. (Ibid.) In Fuentes, our Supreme Court concluded that the proper way to calculate the employer's liability for a new injury causing increased PD is to subtract the percentage of PD suffered as a result of the old injury from that suffered by the sum of both injuries, before consulting the table for the dollar amount of the award. (Brodie, supra, 40 Cal.4th at p. 1322.) This formula, dubbed formula A, had the salutary benefit of treating workers the same regardless of whether previous disabilities were industrial or non-industrial. (See discussion in Brodie, supra, at pp. 1322-1323.) Formula A also encouraged employers to "'. . . hire the handicapped.'" (Ibid.) To develop this formula, Fuentes relied on former sections 4663 and 4750. In 2004 the Legislature repealed sections 4663 and 4750 and enacted Senate Bill No. 899. (Sen. Bill No. 899; Brodie, supra, 40 Cal.4th at p. 1323.) Senate Bill No. 899 revised section 4663 and created section 4664, both of which concern apportionment. (Ibid.) Section 4663 requires physicians to consider apportionment of PD by determining the cause of disability. (Brodie, supra, at pp. 1324-1325) Former section 4663 forbid apportionment by causation. It allowed apportionment if the industrial disease lit up or was aggravated by a nonindustrial injury and permitted increased awards based on the employee's evidence of rehabilitation of an industrial injury for which an award had already been made. (Brodie, supra, 40 Cal.4th at pp. 1326-1327.) The new approach requires consideration of past injuries, not disregard of them. (Id., at p. 1328.) Section 4664 confines the employer's liability to the percentage of disability which is directly caused by the current industrial injury. (Brodie, supra, 40 Cal.4th at p. 1325.) Neither of these provisions specified how disability percentages should be converted into an actual award under section 4658. (Id., at pp. 1325, 1329.) Various Courts of Appeal have reached different conclusions on how apportionment should be calculated. Brodie concluded that formula A, the one approved in Fuentes and discussed above, remains the law. The Brodie court came to this conclusion in large part because there is nothing in Senate Bill No. 899 that expressly or impliedly suggests otherwise. Moreover, the legislative history shows an intent to charge employers only with that percentage of PD directly caused by the current industrial injury. (Brodie, supra, 40 Cal.4th at pp. 1331-1332.)