Which rule best describes the basis for apportioning PD when a subsequent injury occurs?

• A. Apportionment is based on the existence of prior PD at the time of the subsequent injury.
• B. Apportionment is based on the most recent PD award.
• C. Apportionment is based on the current disability rating only.
• D. Apportionment is not applicable to subsequent injuries.

Answer: (A)

When a new injury leads to permanent disability, California law apportions how much of the resulting PD is due to the new injury versus what was already present from a prior condition. The basis for this apportionment is the degree of permanent disability that existed before the subsequent injury occurred. In practice, you assess the pre‑existing PD at the time of the new injury and determine what portion of the current disability can be attributed to that pre-existing condition; that portion is not paid again as PD from the new injury, and only the remaining portion is paid as PD caused by the subsequent injury. This is why the correct choice is based on the existence of prior PD at the time of the subsequent injury.