In Kopping v. Workers' Comp. Appeals Bd. (2006) 142 Cal.App.4th 1099, the injured worker argued: " 'if the Legislature intended section 4664, subdivision (b) to create a conclusive presumption requiring deduction of prior awards by operation of law, what would be the purpose of requiring physicians to calculate the percentage of current permanent disability caused by prior industrial injuries?' " (Id. at p. 1112.) The court responded: "One answer to that question is that section 4664(b) creates a presumption arising from 'a prior award of permanent disability,' not from a prior industrial injury. It is possible that an applicant may have had a prior industrial injury, but never applied for or received an award of permanent disability resulting from that injury. In such a case, in the event of a subsequent industrial injury, the presumption of section 4664(b) would have no effect, but a physician could still determine, as a matter of fact, that the applicant's present level of permanent disability was partially caused by the previous industrial injury." (Ibid.)