"`Wages' mean the average daily wages received by the employee at the time of the injury for the usual hours of employment in a day, and overtime is not to be considered." We considered the term "average daily wage" in Mahlum v. Broeder (1966), 147 Mont. 386, 412 P.2d 572, where we stated: ". . . [T]hat the first step in the formula for compensation is to determine the average daily wage.
¶118 From original enactment in 1915, the Act has been a delicate public policy compromise, with the essential quid pro quo purposes and effects of (1) depriving workers of otherwise available tort remedies (which previously afforded them opportunity for full compensation), in return for some lesser form of guaranteed no-fault compensation for work-related injury, and (2) depriving employers of advantageous common law defenses in tort, in return for limited and predictable liability for employee injuries. See §§ 39-71-105(1), -124, and -411, MCA (2011); Royal Ins. Co. v. Roadarmel , 2000 MT 259, ¶ 29, 301 Mont. 508, 11 P.3d 105 ; Henry v. State Comp. Ins. Fund , 1999 MT 126, ¶ 12, 294 Mont. 449, 982 P.2d 456 ; Sitzman v. Shumaker , 221 Mont. 304, 307, 718 P.2d 657, 659 (1986) ; Madison v. Pierce , 156 Mont. 209, 213-14, 478 P.2d 860, 863 (1970) ; Mahlum v. Broeder , 147 Mont. 386, 392-95, 412 P.2d 572, 575-77 (1966) ; State ex rel. Morgan v. Indus. Accident Bd. of Mont. , 130 Mont. 272, 278-79, 300 P.2d 954, 958 (1956) ; Chisholm v. Vocational Sch. for Girls , 103 Mont. 503, 512-13, 64 P.2d 838, 844 (1936) ; Shea v.North-Butte Mining Co. , 55 Mont. 522, 528-29, 179 P. 499, 501 (1919) ; Lewis & Clark County v. Industrial Accident Bd. , 52 Mont. 6, 9-13, 155 P. 268, 270-71 (1916).
"In the vast majority of cases, this mathematical calculation is based on the four pay periods preceding the injury as reported in the Claim for Compensation and the Employers First Report and there is no dispute. "In Mahlum v. Broeder, 147 Mont. 386, 412 P.2d 572 (1966), the Supreme Court set the standard for defining wages when it was stated: "`. . . What is a reasonable period of time, of course, depends on the circumstances of each case.