What is the test for permanent disability for workers' compensation purposes?

permanent disability for workers' compensation purposes" (Chang v. Workers' Comp. Appeals Bd. (2007) 153 Cal.App.4th 750, 753) for injuries occurring before January 1, 2013. (Stats. 2004, ch. 34, 32; 4660.) Section 4660, subdivision (a) provides that "[i]n determining the percentages of permanent disability, account shall be taken of" four factors, including: (1) "the nature of the physical injury or disfigurement," (2) "the occupation of the injured employee," and (3) "his or her age at the time of the injury," with (4) "consideration being given to an employee's diminished future earning capacity."