Except as otherwise provided in this chapter, the average weekly wage of the injured employee at the time of the injury shall be taken as the basis upon which to compute compensation and shall be determined as follows:

((a)) If the injured employee shall have worked in the employment in which he was working at the time of the injury, whether for the same or another employer, during substantially the whole of the year immediately preceding his injury, his average annual earnings shall consist of three hundred times the average daily wage or salary for a six-day worker and two hundred and sixty times the average daily wage or salary for a five-day worker, which he shall have earned in such employment during the days when so employed.

((b)) If the injured employee shall not have worked in such employment during substantially the whole of such year, his average annual earnings, if a six-day worker, shall consist of three hundred times the average daily wage or salary, and, if a five-day worker, two hundred and sixty times the average daily wage or salary, which an employee of the same class working substantially the whole of such immediately preceding year in the same or in similar employment in the same or a neighboring place shall have earned in such employment during the days when so employed.

((c)) If either of the foregoing methods of arriving at the average annual earnings of the injured employee cannot reasonably and fairly be applied, such average annual earnings shall be such sum as, having regard to the previous earnings of the injured employee in the employment in which he was working at the time of the injury, and of other employees of the same or most similar class working in the same or most similar employment in the same or neighboring locality, or other employment of such employee, including the reasonable value of the services of the employee if engaged in self-employment, shall reasonably represent the annual earning capacity of the injured employee.

((d))

((1)) The average weekly wages of an employee shall be one fifty-second part of his average annual earnings.

((2)) Notwithstanding paragraph (1), with respect to any claim based on a death or disability due to an occupational disease for which the time of injury (as determined under subsection (i)) occurs—

((A)) within the first year after the employee has retired, the average weekly wages shall be one fifty-second part of his average annual earnings during the 52-week period preceding retirement; or

((B)) more than one year after the employee has retired, the average weekly wage shall be deemed to be the national average weekly wage (as determined by the Secretary pursuant to ) applicable at the time of the injury.

((e)) If it be established that the injured employee was a minor when injured, and that under normal conditions his wages should be expected to increase during the period of disability the fact may be considered in arriving at his average weekly wages.

((f)) Effective October 1 of each year, the compensation or death benefits payable for permanent total disability or death arising out of injuries subject to this chapter shall be increased by the lesser of—

((1)) a percentage equal to the percentage (if any) by which the applicable national weekly wage for the period beginning on such October 1, as determined under , exceeds the applicable national average weekly wage, as so determined, for the period beginning with the preceding October 1; or

((2)) 5 per centum.

((g)) The weekly compensation after adjustment under subsection (f) shall be fixed at the nearest dollar. No adjustment of less than $1 shall be made, but in no event shall compensation or death benefits be reduced.

((h))

((1)) Not later than ninety days after , the compensation to which an employee or his survivor is entitled due to total permanent disability or death which commenced or occurred prior to , shall be adjusted. The amount of such adjustment shall be determined in accordance with regulations of the Secretary by designating as the employee’s average weekly wage the applicable national average weekly wage determined under and (A) computing the compensation to which such employee or survivor would be entitled if the disabling injury or death had occurred on the day following , and (B) subtracting therefrom the compensation to which such employee or survivor was entitled on ; except that no such employee or survivor shall receive total compensation amounting to less than that to which he was entitled on . Notwithstanding the foregoing sentence, where such an employee or his survivor was awarded compensation as the result of death or permanent total disability at less than the maximum rate that was provided in this chapter at the time of the injury which resulted in the death or disability, then his average weekly wage shall be determined by increasing his average weekly wage at the time of such injury by the percentage which the applicable national average weekly wage has increased between the year in which the injury occurred and the first day of the first month following . Where such injury occurred prior to 1947, the Secretary shall determine, on the basis of such economic data as he deems relevant, the amount by which the employee’s average weekly wage shall be increased for the pre-1947 period.

((2)) Fifty per centum of any additional compensation or death benefit paid as a result of the adjustment required by paragraphs (1) and (3) of this subsection shall be paid out of the special fund established under , and 50 per centum shall be paid from appropriations.

((3)) For the purposes of subsections (f) and (g) an injury which resulted in permanent total disability or death which occurred prior to , shall be considered to have occurred on the day following such date.

((i)) For purposes of this section with respect to a claim for compensation for death or disability due to an occupational disease which does not immediately result in death or disability, the time of injury shall be deemed to be the date on which the employee or claimant becomes aware, or in the exercise of reasonable diligence or by reason of medical advice should have been aware, of the relationship between the employment, the disease, and the death or disability.