Opinion by Judge SCHROEDER; Partial Concurrence and Partial Dissent by Judge KLEINFELD.
SCHROEDER, Circuit Judge:This epic punitive damage litigation arising from the 1989 wreck of the Exxon Valdez is before us once again. This time it is after the United States Supreme Court remanded the case to us to decide issues related to interest and appellate costs. Order in Exxon Shipping Co. v. Baker, No. 07-219 (S.Ct. filed June 25, 2008).. The remand followed the Court’s 5-3 decision that, under maritime law, the maximum ratio of punitive damages to compensatory damages is 1-1. Exxon Shipping Co. v. Baker, - U.S. -, 128 S.Ct. 2605, 2633, 171 L.Ed.2d 570 (2008). On the issue of the availability of vicarious liability for punitive damages under maritime law, the Court was evenly divided and thus left in place our 2001 decision that punitives are available under precedents binding on this court. Id. at 2616; see In re Exxon Valdez, 270 F.3d 1215, 1233-36 (9th Cir.2001) (citing The Amiable Nancy, 16 U.S. (3 Wheat) 546, 4 L.Ed. 456 (1818); Protectus Alpha Navigation Co., Ltd. v. N. Pac. Grain Growers, Inc., 767 F.2d 1379 (9th Cir.1985)).
The parties have now stipulated to the entry of judgment against the defendant Exxon and in favor of the plaintiffs Baker et al. in the amount of $507.5 million, representing the amount the plaintiffs were awarded as compensatory damages for the income they lost as a result of the massive oil spill. This judgment achieves the 1-1 ratio the Supreme Court deemed appropriate. We delayed issuance of the mandate at the parties’ request and asked for supplemental briefing and argument on the issues the Supreme Court left unanswered: interest and costs.
Interest
The issue with respect to interest is whether interest on the $507.5 million should run from the date of the original judgment, entered in 1996, or whether interest should run only from the 2008 date that we entered judgment for plaintiffs in the wake of the Supreme Court’s decision. Exxon, of course, argues for the later date; plaintiffs, for the earlier.
There is no dispute that post-judgment interest must be awarded, because 28 U.S.C. § 1961 provides that interest:
shall be allowed on any money judgment in a civil case recovered in a district court.... Such interest shall be calculated from the date of the entry of the judgment, at a rate equal to the coupon issue yield equivalent (as determined by the Secretary of the Treasury) of the average accepted auction price for the last auction of fifty-two week United States Treasury bills settled immediately prior to the date of the judgment.
*108028 U.S.C. § 1961 (1994 & Supp. II 1996). The Supreme Court has explained that the “purpose of post-judgment interest is to compensate the successful plaintiff for being deprived of compensation for the loss from the time between the ascertainment of the damage and the payment by the defendant.” Kaiser Aluminum & Chem. Corp. v. Bonjorno, 494 U.S. 827, 835-36, 110 S.Ct. 1570, 108 L.Ed.2d 842 (1990) (quoting Poleto v. Consol. Rail Cotp., 826 F.2d 1270, 1280 (3d Cir.1987)).
The issue here arises because the final $507.5 million judgment of punitive damages represents a substantial reduction of the original district court judgment. Where a damages award has been remitted, Federal Rule of Appellate Procedure 37(b) gives an appellate court discretion as to whether to allow interest to run from the date of the original judgment, or from the date of the remitted judgment. Rule 37(b) specifically provides as follows: “If the [appellate] court modifies or reverses a judgment with a direction that a money judgment be entered in the district court, the mandate must contain instructions about the allowance of interest.” Fed. R.App. P. 37(b).
Interest accrues on the reduced amount, not on the higher amount that was vacated or remitted. Planned Parenthood of Columbia/Willamette Inc. v. Am. Coal. of Life, 518 F.3d 1013 (9th Cir.2008). In Planned Parenthood, we explained the framework for determining the allowance of interest:
Post-judgment interest must run from the date of a judgment when the damages were supported by the evidence and meaningfully ascertained. We may reverse and remand a judgment without concluding that it is erroneous or unsupported by the evidence. When the legal and evidentiary basis of an award is thus preserved, post-judgment interest is ordinarily computed from the date of [the judgment’s] initial entry.
Id. at 1017-18 (internal quotation marks and citations omitted) (alterations in original). Planned Parenthood thus makes it clear that interest ordinarily should be computed from the date of the original judgment’s initial entry when the evidentiary and legal bases for an award were sound. Id.
Exxon contends that the legal basis for an award was not sound in 1996, arguing that until the Supreme Court handed down its 2008 decision in this case, the law did not allow vicarious liability for punitive damages in maritime cases. Yet, an evenly divided Supreme Court left in place our 2001 opinion that punitives were recoverable, and we in turn relied on Supreme Court and Ninth Circuit precedent of long standing. See In re Exxon Valdez, 270 F.3d at 1233-36 (citing The Amiable Nancy, 3 Wheat. 546, 16 U.S. 546, and Protectus Alpha Navigation, 767 F.2d 1379).
We therefore conclude that plaintiffs’ entitlement to punitives was “meaningfully ascertained” when the original district court judgment was entered in 1996. Neither the evidentiary basis for the award nor the legal foundation for an award has been disturbed after nearly a dozen years of subsequent litigation. We see no reason to depart from Planned Parenthood’s general rule in this case. The plaintiffs are entitled to interest from that date on the principal amount they ultimately are entitled to receive, $507.5 million.
As to the rate, the parties agree that the “average accepted auction price for the last auction of fifty-two week United States Treasury bills” was 5.9% on September 12, 1996. See 28 U.S.C. § 1961(a) (1994 & Supp. II 1996). We have no discretion to deviate from § 1961’s instructions on the calculation of interest. See Ford v. Alfaro, 785 F.2d 835, 842 (9th *1081Cir.1986). Interest on the $507.5 million judgment shall, therefore, run from September 24,1996 at the rate of 5.9%.
Costs
Costs have become a point of contention in this case because of the size of the supersedeas security bond that Exxon posted to sustain its appeals, and also because of the length of time the case has taken to reach what we hope is now its conclusion. Thus, Exxon’s total costs approach $70 million. Although Exxon has succeeded in reducing an original jury verdict of $5 billion by about 90%, it remains liable for a far-from-nominal punitive award of more than $500 million.
The controlling rule is Federal Rule of Appellate Procedure 39(a)(4), which provides that where “a judgment is affirmed in part, reversed in part, modified or vacated, costs are taxed only as the court orders.” Plaintiffs point to the last time we issued a mandate on punitives in this case, in 2001, when we ordered each party to bear its own costs. In re Exxon Valdez, 270 F.3d at 1254. The punitive damages award had been remitted at that time as well. Plaintiffs also stress that, in a case of mixed judgment, where each side wins something, this Court usually orders each party to bear its own costs.
Exxon contends that it is essentially the winner of the litigation and that plaintiffs should bear all, or at least 90%, of Exxon’s appellate costs. With some 20/20 hindsight, Exxon now characterizes the course of this case as having been all about the amount of money Exxon would have to pay in punitives. Having reduced that amount by 90%, it declares itself the winner. Yet this ignores the hard-fought, even relentless, battle Exxon waged to avoid any liability for punitives, a battle that resulted in an evenly divided decision by the Supreme Court in 2008 leaving in place our 2001 decision on vicarious liability. Exxon Shipping Co., 128 S.Ct. at 2616.
To bolster its position, Exxon points to the fact that the Supreme Court awarded Exxon its costs. But the default rule before the Supreme Court is that when the lower judgment is vacated, the petitioner gets costs “unless the Court otherwise orders.” Sup.Ct. R. 43.2. Rule 39 contains no such presumption: when a judgment is modified, “costs are taxed only as the court orders.” Fed. R.App. P. 39(a)(4). The dissent does not recognize the difference.
In this case, neither side is the clear winner. The defendant owes the plaintiffs $507.5 million in punitives — according to counsel at oral argument the fourth largest punitive damages award ever granted. Yet that award represents a reduction by 90% of the original $5 billion. In light of this mixed result, and mindful that the equities in this case fall squarely in favor of the plaintiffs — the victims of Exxon’s malfeasance — we exercise our discretion by requiring each party to bear its own costs.
Our decision is in accord with our usual practice when each side wins something and loses something. This court has consistently ordered each party to bear its own costs on appeals where punitive damages are upheld, but reduced. See, e.g., Mendez v. Cty. of San Bernardino, 540 F.3d 1109, 1133 (9th Cir.2008); Planned Parenthood, 422 F.3d at 967; Bains LLC v. Arco Prods., div. of Atl. Richfield Co., 405 F.3d 764, 777 (9th Cir.2005). We have even done so during the course of this litigation, under similar circumstances. See In re Exxon Valdez, 270 F.3d at 1254.
We are aware of two cases concerning reduced punitive damages where a court of appeals affirmed a district court’s divided cost award. See Republic Tobacco Co. v. N. Atl. Trading Co., 481 F.3d 442, 449 (7th Cir.2007); Emmenegger v. Bull Moose *1082Tube Co., 324 F.3d 616, 626-27 (8th Cir. 2003). Whether a district court abuses its discretion in awarding costs under similar circumstances is quite different from the question of whether we should exercise our own discretion in that manner. Moreover, if we were to apportion costs on the basis of Exxon’s proposed mathematical formula, i.e., to match the costs awarded to the percentage reduction of damages achieved during the appellate process, we would be inviting increased and wasteful litigation over the apportionment of costs. We see no reason to enter such a thicket, and that the dissent has found only one thirty-year-old out-of-circuit case adopting a similar approach validates our decision that it would be unwise to do so.
Conclusion
Because the evidentiary and legal bases for the original judgment of punitive damages have not been overruled, we award interest on the final judgment of $507.5 million, at the statutorily set rate of 5.9%, to run from the date of the original judgment, September 24, 1996. Because the amount of the original $5 billion judgment has been substantially reduced, we order that each party bear its own costs.
The case is remanded to the district court for entry of the final judgment in accordance with this opinion.