Does your client's disability rating = earning capacity loss?

Maybe, Maybe not. Like most personal injury cases, it depends on the injury.

The key to establishing the presence of an earning capacity disability is (are) the functional limitations that have been imposed on an individual as a result of a permanent impairment. In otherwords, for some persons a 25% whole body impairment may result in a greater than 25% loss of earnings capacity. For other injuried individuals, the loss in earnings capacity may be less.

Functional limitations may preclude someone from performing the functional exertional demands of certain kinds of jobs, thus establishing a loss of earning capacity.
In most instances, there is no direct one to one correlation between permanent impairment and loss of earning capacity aside from the perception that for purposes of general damages one might argue that the higher the percentage of permanent impairment, the greater the loss of earning capacity.