The most current one if looking at it today; or the one in effect at the time of review.
Disclaimer Information on this site is provided by Brian Scott Wayson as general information, not legal advice, and use of this information does not establish an attorney-client relationship. If you have questions about your specific situation, please call an attorney.
It depends what state you're in.
In California, we use AMA Guides to the Evaluation of Permanent Impairment, Fifth Edition.
This answer should not be interpreted as creating an attorney-client privilege, or as legal advice.