We granted certiorari to review the unpublished opinion of the Colorado Court of Appeals in
Marinez v. Industrial Commission,
No. 85CA1534 (Colo.App.1986), in order to determine whether our decision in
Engelbrecht v. Hartford Accident & Indemnity Co.,
We agree with the petitioner that our decision in Engelbrecht should be applied retroactively. Therefore, we reverse the judgment of the court of appeals.
I.
On March 19, 1976, the petitioner, Nativi-dad F. Marinez, was involved in an automobile accident while in the course and scope of his employment. As a result of the accident, Marinez was rendered a paraplegic from the waist down. The State Cоmpensation Insurance Fund (State Fund), the employer’s workers’ compensation insurer, admitted that Marinez was permanently and totally disabled and admitted liability for compensation. Marinez was accordingly awarded state workers’ compensation periodic disability benefits payable for the remainder of his life. See § 8-51-107, 3B C.R.S. (1986). On September 1, 1976, Mari-nez also began receiving periodic social security disability benefits. The State Fund immediately began deducting $39.70 per week, constituting one-half of the social security disability payments, from Mari-nez’s workers’ compensation disability payments pursuant to section 8-51-101(l)(c), 3B C.R.S. (1986). On June 1,1977, Marinez received a cost-of-living increase in his social security disability benefits, and the State Fund began deducting one-half of this increase from his workers’ compensation disability benefits as well.
On May 1, 1984, approximately one week after we announced our decision in Engel-brecht, the State Fund ceased making deductions from Marinez’s workers’ compensation disability benefits based on the social security cost-of-living increases. Thereafter, on May 18, 1984, Marinez filed an application with the Department requesting a hearing to determine whether he should be reimbursed for the money previously deducted from his workers’ compensation disability benefits based on cost-of-living increases in his social security disability benefits. A hearing was held before a hearing officer. The hearing officer concluded that Engelbrecht should be applied *555 prospectively only, and therefore entered an order denying Marinez’s request for reimbursement for the social security cost-of-living deductions. The Commission entered an order adopting and affirming the hearing officer’s decision on October 16, 1985.
Marinez appealed the Commission’s order to the court of appeals. That court affirmed the order, relying on
Rusk v. Industrial
Commission,
II.
In
Engelbrecht v. Hartford Accident & Indemnity Co.,
In cases where it is determined that periodic disability benefits granted by the federal old-age, survivors, and disability insurance act are payable to an individual and his dependents, the aggregate benefits payable for temporary total disability, temporary partial disability, permanent partial disability, and permanent total disability pursuant to this section shall be reduced, but not below zero, by an amount equal as nearly as practical to one-half such federal periodic benefits ....
We held that to interpret the phrase “periodic disability benefits” in section 8-51-101(l)(c) to include cost-of-living increases in social security disability payments would not be consistent with the purposes of the
Workmen’s Compensation Act, sections 8-40-101 to 8-54-127, 3B C.R.S. (1986 & 1987 Supp.), “to protect employees who suffer injuries arising out of their employment and to give injured workers a reliable source of compensation.”
Engelbrecht,
[A] cost-of-living increase [in federal social security disability benefits] does not result in a double award. The federal government has decided that it will maintain the buying power of social security payments, not that it will provide additional benefits for a particular injury. Because Colorado does not provide benefits to keep pace with inflation, there is no double payment.
Id. Finally, we noted that “allowing an insurer to deduct оne-half the cost-of-living increase each time one occurs, and thus decrease the amount the insurer owes, is not consistent with the goal [of the Workmen’s Compensation Act] of determining with certainty the amount owed.” Id.
Therefore, we held that cost-of-living increases in social security disability benefits may not be deducted from workers’ compensation disability benefits pursuant to section 8-51-101(l)(c). However, we did not address whether our holding was to be applied only prospectively — to payments to be made subsequent to the date of our decision — or retroactively as well — to all past payments from which such deductions had been taken. We turn now to the resolution of that issue.
III.
A.
“[T]he federal constitution has no voice upon the subject” of retroactivity,
*556
and state courts are therefore free to choose whether to apply new state court rulings retroactively or prospectively.
Great Northern Ry. Co. v. Sunburst Oil & Ref. Co.,
In
Chevron Oil Co. v. Huson,
In
People in the Interest of C.A.K.,
The United States Supreme Court in
Chevron
provided no specific guidance regarding the interrelationship of the three factors by which a retroactivity issue is to be resolved. Instead, the Court analyzed each factor separately and concluded that each favored a prospective application of the rule at issue in that case.
Chevron,
In People in the Interest of C.A.K., we determined that the Chevron factors should be applied in the following manner:
First, the decision, if it is not to be applied retroactively, must establish a new rule of law. Second, the merits of each case must be weighed by looking to the purpose and effect of the rule in question and whether retrospective operation will further or retard its operation. Third, *557 the inequity imposed by retroactive application must be weighed to avoid injustice or hardship.
People in the Interest of C.A.K.,
People in the Interest of C.A.K. established that the question of retroactivity arises only when a decision establishes a new rule of law. 4 When that condition has been met, the factors favoring and disfavoring retroactive application are to be weighed in the balance. All do not necessarily have equal weight but are to be evaluated on the basis of the strength of the equitable and policy considerations underlying each. We follow this approach in resolving the retroactivity issue in the case now before us.
B.
1.
We begin with the first part of the
Chevron
test, whether our decision in
Engel-brecht
established a new principle of law. As we noted in
Engelbrecht,
cost-of-living increases to social security benefits were first authorized by Congress in 1972 and were first paid in 1975.
Engelbrecht,
The statute itself does not explicitly resolve the question decided in
Engelbrecht.
Pending definitive judicial interpretation, it was necessary that insurers obligated for periodic disability payments under section 8-51-101(l)(c) act based upon their own considered understanding of the statute’s requirements. As the parties agree, the prevalent if not uniform practice of such
*558
insurers was to treat cost-of-living increases to social security disability benefits as “periodic disability benefits” and therefore to deduct one-half of such increases from workers' compensation disability benefit payments. In
Engelbrecht,
we rejected the statutory interpretation upon which that practice was based and determined that such deductions were improper.
Engel-brecht
did not overrule past precedent.
6
However,
Engelbrecht
did construe for the first time a statute that was not explicit in its application to cost-of-living increases in social security disability payments, and our construction was contrary to the one that insurers had applied to govern the computation of periodic disability payments under section 8-51-101(l)(c). It cannot be said that the statute is so plain that the construction adopted in
Engelbrecht
was “clearly foreshadowed,”
Chevron,
2.
The establishment of a new principle of law, however, is only the threshold factor in the Chevron analysis. We next examine the merits and demerits of retroactive application of the Engelbrecht decision by looking to the history of cost-of-living adjustments, the purpose and effect of our rule in Engelbrecht, and whether retroactive operation of Engelbrecht will further or retard the operation of that rule.
As earlier noted, Congress provided for cost-of-living increases to social security benefits in 1972, presumably to maintain the purchasing power of those payments in an inflationary economy.
See Engelbrecht,
Among the purposes of the Workmen’s Compensation Act are the protection of employees who suffer injuries arising out of their employment and the provision of a reliable source of compensation to those injured workers.
Engelbrecht,
Retroactive application of Engelbrecht would further both its purpose and its effect. Before Engelbrecht, those workers, including the petitioner, whose workers’ compensation disability benefits were decreased because of cost-of-living increases in federal benefits effectively received only one-half of the cost-of-living increase deemed necessary by Congress to permit social security periodic disability payments to keep pace with inflation. Not only did *559 Colorado not provide for cost-of-living increases of its own, but it in effect deprived the injured worker of one-half of the increase provided under federal law. Applying Engelbrecht retroactively would redress that inequity and would accord to the affected injured workers the full intended benefit of past cost-of-living increases to social security disability payments. Granting workers the full benefit of the cost-of-living increases would more nearly stabilize the purchasing power of the payments and thereby promote the statutory purposes of protection of injured employees and provision of a reliable source of income, without resulting in double payments for the same injury.
The State Fund contends, however, that a retroactive application of Engel-brecht would undermine the planning upon which the success of the state compensation scheme rests and would jeopardize the financial stability of the insurance system. This in turn would threaten the very source of the payments that now protect injured workers and assure them a reliable source of income. Therefore, argues the State Fund, the purpose of Engelbrecht would be retarded by retroactive application of that case.
The State Fund, however, offered no evidence to support its argument that retroactive application of
Engelbrecht
would jeopardize the financial stability of the insurance system. We have no basis, therefore, to evaluate the extent of the obligations that would result from a retroactive application of
Engelbrecht
or the adequacy of the reserves of insurers to meet such obligations. It is the State Fund’s burden to prove its assertion that financial stability of the insurance system is at stake.
See Jimenez v. Weinberger,
3.
We turn now to the third factor in Chevron, whether inequity, resulting in injustice or hardship, would follow from the retroactive application of Engelbrecht. From the perspective of injured workers, of course, quite the contrary is the case. Until our decision in Engelbrecht workers were wrongfully deprived of a portion of their just benefits because of an erroneous interpretation of the law by insurers. Requiring the wrongfully withheld amounts to be paid to injured workers would do no more than make them whole.
We recognize, however, as the State Fund contends, that the insurance industry and state compensation system have relied on their interpretation of section 8-51-101(l)(c) since cost-of-living increases to federal -social security disability benefits were instituted. We also recognize that practical considerations must be evaluated when determining whether to apply а decision retroactively.
Ground Water Comm’n v. Shanks,
Once again, however, the record is insufficient to address the State Fund’s contentions. The record contains no information regarding the number of workers who would be affected by a retroactive application, the amount of money to be paid, the size of reserves out of which payments would be paid, the degree to which insurers have relied on cost-of-living deductions, or the administrative burden of reprocessing applications. It is the State Fund’s burden to prove its contention that serious adverse consequences to insurers would result from retroactive application of
Engelbrecht. See Jimenez,
523 F.2d at
*560
704;
Hurvich,
4.
In summary, we conclude that En-gelbrecht established a new principle of law by resolving as a matter of first impression that under section 8-51-101(l)(c) workers’ compensation carriers may not deduct cost-of-living increases in social security disability benefits from state periodic disability payments. We further conclude that the purpose and effect of the Engel-brecht rule will be furthered by a retroactive application. No showing has been made that a retroactive application would impose inequities on insurance carriers or would jeopardize the financial stability of the workers’ compensation scheme. Therefore, we hold that Engelbrecht should be applied retroactively to the petitioner’s claim.
The judgment of the court of appeals is reversed and the case is remanded to that court to be returned to the Commission for further proceedings consistent with the views expressed in this opinion. 8
Notes
. After we granted certiorari in
Rusk
v.
Industrial Commission,
. The Court described the factors to be considered as follows:
[W]e must ... weigh the merits and demerits in each case by looking to the prior history of the rule in question, its purpose and effect, and whether retrospective operation will further or retard its operation.
Linkletter,
. Lacking definitivе guidance from the United States Supreme Court, the lower federal courts have developed at least three different methods of applying the Chevron factors. See Note, Confusion in Federal Courts: Application of the Chevron Test in Retroactive-Prospective Decisions, 1985 U.Ill.L.Rev. 117, 132-38 (1985). The three methods are the threshold method, the balancing method, and the comprehensive method. Under the threshold method, a retroactive-prospective question exists only when a court announces an unforesеeable new rule. If the court determines that a new rule was announced, then it must balance the second and third factors. If the court concludes that the rule in question is not new, the rule is to be applied retroactively without further inquiry. The balancing method, as its name implies, requires a balancing of the three factors, and involves a subissue of the weight to be given to each. Finally, the comprehensive method requires all three Chevron factors to favor nonre-troactivity before a new rule may be given only prospective application. Id. at 133-36.
. As Justice Stewart, the author of the Chevron opinion, has stated:
An issue of the "retroactivity” of a decision of this Court is not even presented unless the decision in question marks a sharp break in the web of the law. The issue is presented only when the decision overrules clear past precedent or disrupts a practice widely relied upon.
Milton v. Wainwright,
. In
Engelbrecht,
we reviewed two decisions of the court of appeals,
Dailey
v.
Industrial Commission,
. The court of appeals judgments that were reversed in Engelbrecht were not final in that they were under review by certiorari. Therefore, the reversal of those judgmеnts did not constitute the overruling of prior precedent.
. In
Jeffrey v. Colorado State Department of Social Services,
. The court of appeals directed the Commission on remand to consider the petitioner’s request to amend his average weekly wage and contest the wage admitted by respondents. Marinez v. Industrial Comm’n, No. 85CA1534, slip op. at 2 (Colo.App.1986). Our grant of certiorari did not include this issue. The Commission must comply with the court of appeals’ directive on this subject when the case is returned to the Commission for further proceedings.
