77 Pa. Stat. § 1409
Whenever in this article the term "wages" is used, it shall be construed to mean the average weekly wages of the employe ascertained as follows:
If the employe has been in the employ of employer less than thirteen calendar weeks, (or three calendar months if the employe receives wages monthly, or semi-monthly) immediately preceding the disability, his average weekly wage shall be computed under the foregoing paragraph, taking "total wages" for such purpose to be the amount he would have earned had he been so employed by employer the full thirteen calendar weeks, (or three calendar months) immediately preceding the disability, and had worked when work was available to other employes in a similar occupation, unless it be conclusively shown that, by reason of exceptional causes, such method of computation does not ascertain fairly the "total wages" of the employe so employed less than thirteen calendar weeks (or three calendar months).
The terms "average weekly wage" and "total wages", as used in this section, shall include board and lodging received from the employer, and when so received, the board shall be rated at two dollars per day if more than one meal is served, and one dollar per day if only one meal is served, and lodging shall be rated at one dollar and fifty cents per day. In employments in which employes customarily receive not less than one-third of their remuneration in tips or gratuities not paid by the employer, gratuities shall be added to the wages received at the rate of two dollars per day; but such terms shall not include amounts deducted by the employer under the contract of hiring for labor furnished, or paid for by the employer, and necessary for the performance of such contract by the employe nor shall such terms include deductions from wages due the employer; for rent, and supplies necessary for the employe's use in the performance of his labor.
Where the employe is working under concurrent contracts with two or more employers, and the defendant employer has knowledge of such employment prior to the disability, his wages from all such employers shall be considered as if earned from the employer liable for compensation.
If under clauses (a), (b), (c), (d) and (e) of this section the amount determined is less than if computed as follows, this computation shall apply, viz: divide the total wages earned by the employe during the last two completed calendar quarters with the same employer by the number of days he worked for such employer during such period multiplied by five.
The weekly wage upon which compensation shall be computed, shall be the wage earned by the employe in his last employment in the occupation or industry in which the occupational disease is a hazard.
77 P.S. § 1409