Opinion of the Court (to determine lost wage-earning capacity, juries must often "use their judgment (in effect, . . . speculate)"). That juries in tort cases must routinely engage in such difficult predictions (compounded further by discounting for present value) is the price paid by the common-law approach for the finality of a one-time lump-sum judgment. The second possible way to account for future developments would be to do in this situation just what the Act already does through the modification provision in the run of cases: to wait and see, that is, to base calculation of diminished wage-earning capacity, and thus compensation, on current realities and to permit modifications reflecting the actual effects of an employee's disability as manifested over time. This way, finality is exchanged for accuracy, both in compensating a worker for the actual economic effects of his injury, and in charging the employer and his insurer for that amount alone. Metropolitan denies that the second, wait-and-see alternative is even open, arguing that §8(h) gives the factfinder only two choices: either deny compensation altogether because a claimant's actual wages have not diminished, or, if the ALJ concludes that the worker's current income does not fairly represent his present wage-earning capacity, calculate the annual earnings of $60,000, and a 25% chance of being laid off from that job and remaining unemployed with no income because his injuries would prevent him from performing more strenuous work, for a weighted average future wage-earning capacity of $45,000. (($60,000.75)+($0.25) =$45,000.) Of course, even if the factfinder somehow got the probabilities and earnings for each possible future state right, the weighted average future capacity would rarely correspond to actual developments. In our hypothetical, Rambo's actual future capacity would be $15,000 a year more than his predicted capacity if he kept his job as a crane operator, and $45,000 less if he lost that job and found no other. Thus, if a compensation award were based on the weighted average, Rambo would necessarily end up either overcompensated or undercompensated, even though the Act might meet its objectives for the system as a whole. Opinion of the Court extent of the worker's disability (and his consequent entitlement to compensation) in toto based on all relevant factors, including the future effects of the disability. See Brief for Petitioner 9. What we have already said, however, shows the unsoundness of Metropolitan's two options. 6 The practical effect of denying any compensation to a disabled claimant on the ground that he is presently able to earn as much as (or more than) before his injury would run afoul of the Act's mandate to account for the future effects of disability in fashioning an award, since those effects would not be reflected in the current award and the 1-year statute of limitations for modification after denial of compensation would foreclose responding to such effects on a wait-andsee basis as they might arise. On the other hand, trying to honor that mandate by basing a present award on a comprehensive prediction of an inherently uncertain future would, as we have seen, almost always result in present overcompensation or undercompensation. And it would be passing strange to credit Congress with the intent to guarantee fairness to employers and employees by a wait-and-see approach in most cases where future effects are imperfectly foreseeable, but to find no such intent in one class of cases, those in which wage-earning ability does not immediately decline.7 6 The one possible escape from this conclusion rests on an implausible reading of the Act. A claimant could, arguably, preserve a right to compensation in the future by reapplying within the 1-year period and successively each year thereafter. See § 22, 33 U. S. C. § 922 (permitting modification "at any time prior to one year after the rejection of a claim"). But this would be a strange way to administer the Act, for its very premise is that a claimant would repeatedly file reapplications knowing his disability to be without present effect and (on Metropolitan's theory) himself without any good-faith claim to the present compensation sought. 7 The legislative history to the 1938 amendments to the Act, which added §8(h), indicates that Congress understood that the reference to future effects in the new subsection would interact with § 22 by allowing compensation for permanent partial disability for employees whose job opportunities are narrowed by injury but whose wages have not declined: Opinion of the Court There is moreover an even more fundamental objection to Metropolitan's proposed options. They implicitly reject the very conclusion required to make sense of the combined provisions limiting claims and mandating consideration of future effects: that a disability whose substantial effects are only potential is nonetheless a present disability, albeit a presently nominal one. It is, indeed, this realization that points toward a way to employ the wait-and-see approach to provide for the future effects of disability when capacity does not immediately decline. It is simply "reasonable” and “in the interest of justice" (to use the language of § 8(h)) to reflect merely nominal current disability with a correspondingly nominal award. Ordering nominal compensation holds open the possibility of a modified award if a future conjunction of injury, training, and employment opportunity should later depress the worker's ability to earn wages below the preinjury level, turning the potential disability into an actual one. It allows full scope to the mandate to consider the future effects of disability, it promotes accuracy, it preserves administrative simplicity by obviating cumbersome enquiries relating to the entire range of possible future states of affairs, and it avoids imputing to Congress the unlikely intent "[Section 8(h)] provides for consideration of the effects of an injury . . . upon the employee's future ability to earn. . . . Often an employee returns to work earning for the time being the same wages as he earned prior to injury, although still in a disabled condition and with his opportunity to secure gainful employment definitely limited. . . . It is clear that in such a case the employee's ability to compete in the labor market has been definitely affected; and, though at present the employee is paid his former full-time earnings, he suffers permanent partial disability which should be compensable under the... Act.... "In a case such as that. . ., an unscrupulous employer might with profit to himself continue the original wages... until the ... right of review of the case (sec. 22) had run, . . . thus defeat[ing] the beneficent provisions of the.. Act." H. R. Rep. No. 1945, 75th Cong., 3d Sess., 5-6 (1938); S. Rep. No. 1988, 75th Cong., 3d Sess., 1 (1938). 8 See Walters v. Metropolitan Ed. Enterprises, Inc., 519 U. S. 202, 208, 210-211 (1997) (weighing administrative simplicity in favor of permissible construction of statute). Opinion of the Court to join a wait-and-see rule for most cases with a predict-thefuture method when the disability results in no current decline in what the worker can earn. Our view, as it turns out, coincides on this point with the position taken by the Director of the Office of Workers' Compensation Programs (OWCP), who is charged with the administration of the Act, and who also construes the Act as permitting nominal compensation as a mechanism for taking future effects of disability into account when present wageearning ability remains undiminished. See Brief for Director, Office of Workers' Compensation Programs 12–21, 24–31. The Secretary of Labor has delegated the bulk of her statutory authority to administer and enforce the Act, including rulemaking power, to the Director, see Director, Office of Workers' Compensation Programs v. Newport News Shipbuilding & Dry Dock Co., 514 U. S. 122, 125-126 (1995); Ingalls Shipbuilding, Inc. v. Director, Office of Workers' Compensation Programs, 519 U. S. 248, 262-263 (1997), and the Director's reasonable interpretation of the Act brings at least some added persuasive force to our conclusion, see, e. g., Skidmore v. Swift & Co., 323 U. S. 134, 140 (1944) (giving weight to agency's persuasive interpretation, even when agency lacks "power to control"); Robinson v. Shell Oil Co., 519 U. S. 337, 345-346 (1997). There is, of course, the question of how high the potential for disability need be to be recognized as nominal, but that is an issue not addressed by the parties, and it would be imprudent of us to address it now with any pretense of settling it for all time. Here it is enough to recall that in those cases where an injury immediately depresses ability to earn wages under present conditions, the payment of actual compensation holds open the option of modification under §22 even for future changes in condition whose probability of occurrence may well be remote at the time of the original award. Consistent application of the Act's wait-and-see approach thus suggests that nominal compensation permitting Opinion of the Court future modification should not be limited to instances where a decline in capacity can be shown to a high degree of statistical likelihood. Those courts to have dealt with the matter explicitly have required a showing that there is a significant possibility that a worker's wage-earning capacity will at some future point fall below his preinjury wages, see Hole v. Miami Shipyards Corp., 640 F. 2d 769, 772 (CA5 1981); Randall v. Comfort Control, Inc., 725 F. 2d 791, 800 (CADC 1984), and, in the absence of rulemaking by the agency specifying how substantial the possibility of future decline in capacity must be to justify a nominal award, we adopt this standard.9 9 The OWCP Director argues that when the employee has the burden of persuasion, the Administrative Procedure Act's (APA's) preponderance of the evidence standard (see infra, at 139) requires him to show that an injury-related future decline in wages is more likely than not to occur. Brief for Director, Office of Workers' Compensation Programs 22-23. The Director's position confuses the degree of certainty needed to find a fact or element under the preponderance standard with the fact or element to be so established, which in this case is the statistical odds that wageearning capacity will decline in the future. "The burden of showing something by a preponderance of the evidence . . . simply requires the trier of fact to believe that the existence of a fact is more probable than its nonexistence before [he] may find in favor of the party who has the burden to persuade the [judge] of the fact's existence." Concrete Pipe & Products of Cal., Inc. v. Construction Laborers Pension Trust for Southern Cal., 508 U. S. 602, 622 (1993) (internal quotation marks omitted). In other words, the preponderance standard goes to how convincing the evidence in favor of a fact must be in comparison with the evidence against it before that fact may be found, but does not determine what facts must be proven as a substantive part of a claim or defense. See Greenwich Collieries v. Director, OWCP, 990 F. 2d 730, 736 (CA3 1993) ("A preponderance of the evidence is ... [e]vidence which is . . . more convincing than the evidence offered in opposition to it . . ." (internal quotation marks omitted)), aff'd, 512 U. S. 267 (1994). Unlike other standards of proof such as reasonable doubt or clear and convincing evidence, the preponderance standard "allows both parties to share the risk of error in roughly equal fashion,' Herman & MacLean v. Huddleston, 459 U. S. 375, 390 (1983) (internal quotation marks omitted), except that "when the evidence is evenly balanced, the [party with the burden of persuasion] must lose," Director, Of |