delivered the opinion of the court.
Earl A. Bemis, an employee of Texaco, was injured by an industrial accident on May 29, 1954. X ray revealed a compression fracture of the interior part of the eighth dorsal body. This fracture was reported well healed by January 22, 1955, and employee was discharged from treatment March 1955. On October 17, 1963, reexamination showed that increased arthritic changes in the 1954 fracture caused a 17 percent disability of the employee’s body. In December 1963 Bemis filed an application and claim for award under the Workmen’s Compensation Law for 17 percent permanent partial disability, and Texaco approved the claim for $2,040, such amount being based on the provisions of c. 204, § 3, S.L. of Wyoming, 1961. At the instance of the Workmen’s Compensation Department and the State Treasurer, the amount was reduced to $1,275, it being their position that the applicable law was c. 143, § 40, S.L. of Wyoming, 1951, and the employee appealed.
Appellant contends that the order entered by the trial court, which reduced the amount, should be reversed because:
(1) The district court did not have jurisdiction to enter the order appealed from as the State Treasurer did not file a petition to reopen the case as required by law, and if a proper petition were filed it was not filed within thirty days after receipt of the order of award as required by law; and
(2) The compensable injury did not occur at the time of the accident, but occurred in *530 1963 when arthritic changes caused a 17 percent permanent partial disability.
In Claim of Heil,
In Warner v. Zaiser,
“ * * * The obligations and rights of the parties as to weekly compensation and other benefits to the employee do become fixed at the date of a com-pensable accident * * *. The rate of compensation * * * for injury * * * may not be changed after the event takes place that fixes the rights of the parties under the law in force at that particular time.” (Emphasis supplied.)
Problems have often arisen on a somewhat allied subject, that is, whether Workmen’s Compensation in force at the time of an accident or that at the time of a workman’s resulting death determines the compensation recoverable by a dependent. In this there has been little unanimity of agreement. Annotation,
Appellant cites as authority for his position Allen v. Kalamazoo Paraffine Co.,
We recognize the well established rule that statutes are not to be applied retroactively unless so provided therein, and this is especially true when substantive rights of parties are involved. Claim of Heil, supra. Nevertheless, in instances where employment has continued until the time of actual disability, we must hold that, where disability becomes a fact after a change *531 in compensation rates, such changes have become an integral part of the employment status. This, of course, is not to say that the actual time of disability and the cause thereof is not a matter of proof- — the burden of which would be upon the employee. Although the appellee now argues that the only event which took place in 1963 was that a determination was made relative to the degree of the appellant’s disability, this was not a matter raised before the trial court.
This court’s holding that where disability becomes a fact after a change in compensation rates, such changes have become an integral part of the employment status, makes unnecessary any discussion regarding appellant’s contention that the district court did not have jurisdiction to enter the order appealed from.
Reversed.
