D.C. Code 36-308 (3) (1997 Repl.) sets forth the method through which a "disability partial in character but permanent in quality" is to be compensated. The Act defines a disability as a "physical or mental incapacity because of injury which results in the loss of wages." D.C. Code 36-301 (8) (1997 Repl.). Reading these two provisions together, a disability is partial when it is the result of an injury causing some, but not an entire, loss of wages. A disability is permanent if the employee will suffer at least some loss of wages which he will not regain due to the injury. Section 36-308 (3) establishes two separate bases for compensating employees who have suffered a permanent disability. Section 36-308 (3)(A) through (U) establishes a schedule of awards. Under that provision, an employee suffering a permanent disability will receive an award for any injury specifically listed (a "schedule injury") in addition to any compensation for temporary total or partial disability. D.C. Code 36-308 (3). When an employee suffers a schedule injury, the employee will receive a sum consisting of 66 2/3% of his average weekly wage multiplied by the number of weeks set forth in the Act for the particular injury. Thus, for example, an employee who suffers the loss of an arm (a schedule injury) will receive 66 2/3% of his weekly wage multiplied by 312 weeks. D.C. Code 36-308 (3)(A). By contrast, when an employee suffers a permanent loss of earnings due to an injury, but has not suffered an injury listed in sections (A) through (U) (i.e., a schedule injury), section (V) sets forth the rate of compensation: The compensation shall be 66 2/3% of the greater of: (I) the difference between the employee's actual wage at the time of injury and the average weekly wage, at the time of injury, of the job that the employee holds after the employee becomes disabled; or (II) the difference between the average weekly wage, at the time the employee returns to work, of the job that the employee held before the employee became disabled and the actual wage of the job that the employee holds when the employee returns to work. D.C. Code 36-308 (3)(V)(ii) (1997 Repl.). To receive an award under this section, therefore, the employee must suffer an actual loss of wages. Washington Metro. Area Transit Auth. v. District of Columbia Dep't of Employment Servs., 683 A.2d 470, 473 (D.C. 1996) ("WMATA"). "Disability is an economic and not a medical concept." Washington Post v. District of Columbia Dep't of Employment Servs., 675 A.2d 37, 40 (D.C. 1996) (citing American Mut. Ins. Co. v. Jones, 138 U.S. App. D.C. 269, 271, 426 F.2d 1263, 1265 (1970)).