Impairment reflects a “a significant deviation, loss, or loss of use of any body structure or body function in an individual with a health condition, disorder, or disease” and is not synonymous with disability, which refers to “activity limitations and/or participation restrictions in an individual with a health condition, disorder, or disease.” The American Medical Association Guides to the Evaluation of Permanent Impairment are the most widely used standard to assess impairment. Future research could use empirical evidence on the relationship between impairment ratings and earnings losses to improve the ability of the Guides to predict the economic consequences of a disabling injury.