(1) The average wage applicable to the calculation of compensation, etc. for the employee pursuant to Articles 79, 80, and 82 through 84 of the Act shall, when the average amount of monthly ordinary wage per employee (hereinafter referred to as the "average amount") paid to employees in the same business category in the same business or workplace to which the relevant employee belongs has changed by at least five percent from the average amount paid in the month when an injury or a disease occurs, be such amount increased or decreased at the aforesaid rate of change, but such rate shall apply to the month immediately following the month of occurrence of grounds for change and the months subsequent thereto: Provided, That the second or latter adjustment of average wages shall be calculated based on the average amount of the month in which a cause for immediately preceding change occurred.
(2) Where the business or workplace to which the relevant employee belongs is permanently closed down, the adjustment of average wage under paragraph (1) shall be based on a business or workplace with the same business type and scale as at the time when an occupational injury or disease was inflicted on the employee.
(3) If there is no employee engaged in the same occupational category as the relevant worker, the adjustment of the average wage under paragraph (1) or (2) shall be based on employees engaged in the occupation of similar category.
(4) The average wage applicable to the computation of the retirement benefits under Article 8 of the Act on the Guarantee of Employees' Retirement Benefits, which shall be paid to an employee who suffers from an occupational injury or disease in accordance with Article 78 of the Act, shall be the average wage adjusted in accordance with paragraphs (1) through (3).