In Escobedo v. Marshalls (2005) 70 Cal.Comp.Cases 604, the WCAB en banc explained that apportionment under former section 4663 required substantial evidence that permanent disability would have occurred no later than the permanent and stationary date from the natural progression of the non-industrial condition or disease absent industrial injury. Under amended section 4663, the reporting physician is required to address apportionment of disability based on causation that differs from causation of the injury and provide percentages of disability caused by the industrial injury versus other factors. The other factors may include factors that formerly could not support apportionment, such as pathology, including degenerative disease of a joint, asymptomatic prior conditions, and retroactive prophylactic conditions. The injured worker has the burden to prove the percentage of disability caused by the industrial injury, and the employer has the burden to prove the percentage of disability caused by other factors.