The sixth edition of the American Medical Association's Guides to the Evaluation of Permanent Impairment (AMA Guides), published in December 2007, introduced new approaches to rating impairment, often a starting point in determining permanent partial disability awards in workers compensation. This research study analyzes the impact on impairment ratings in three states due to the switch from the fifth edition of the AMA Guides to the sixth edition.
The results of this study provide evidence that a decrease in the average impairment rating is realized when a state switches from the fifth edition to the sixth edition of the AMA guides, all else being equal. After controlling for claim maturity, the three states studied show:
- In Montana, the average impairment decreased by approximately 28%
- In Tennessee, the average impairments decreased by approximately 25% and 16% for whole body and part of body, respectively
- In New Mexico, the average impairments decreased by approximately 32% and 6% for whole body and part of body, respectively
An analysis of states that did not switch editions suggests that the above changes in the average impairment ratings may be impacted to some degree by factors unrelated to which edition of the AMA Guides was used to rate impairment.
For those states that switch, or plan on switching, from the fifth edition to the sixth edition, the impact on a state's workers compensation costs will vary based on changes in the average impairment and/or disability ratings, along with the percentage of statewide benefits attributable to permanent partial disability benefits.