What is the test for determining the percentage of permanent disability for an employee who suffers from multiple sclerosis?

"In determining the percentages of permanent disability, account shall be taken of the nature of the physical injury or disfigurement, the occupation of the injured employee, and his or her age at the time of the injury, consideration being given to an employee's diminished future earning capacity." (Lab. Code, 4660, subd. (a), italics added.) The purpose of considering the employee's occupation is "to aid in determining 'the relative effects of disability to various parts of the body taking into account the physical requirements of various occupations.' " (Holt v. Workers' Comp. Appeals Bd. (1986) 187 Cal.App.3d 1257, 1261 (Holt).)