¶53 (concurring/dissenting) — While I concur in upholding the jury’s verdict for the provider class, I dissent as to the reversal of the trial court’s award of prejudgment interest. Awarding prejudgment interest on the contract damages due to the provider class in this case is consistent with Washington case law and its underlying policy. I would therefore affirm the award.
¶54 The lead opinion correctly states the rule on when prejudgment interest is warranted but misapplies it, failing to adhere to our prior cases. The rule is that prejudgment interest is available
(1) when an amount claimed is “liquidated” or (2) when the amount of an “unliquidated” claim is for an amount due upon a specific contract for the payment of money and the amount due is determinable by computation with reference to a fixed standard contained in the contract, without reliance on opinion or discretion.
Prier v. Refrigeration Eng’g Co., 74 Wn.2d 25, 32, 442 P.2d 621 (1968). A claim is liquidated “where the evidence furnishes data which, if believed, makes it possible to compute the amount with exactness, without reliance on opinion or discretion.” Prier, 74 Wn.2d at 32; see 1 Dan B. Dobbs, Dobbs Law of Remedies § 3.6(1), at 337 (2d ed. 1993) (citing Hansen v. Rothaus, 107 Wn.2d 468, 472-73, 730 P.2d 662 (1986)).
¶55 This case is remarkably similar to Stevens v. Brink’s Home Security, Inc., 162 Wn.2d 42, 169 P.3d 473 (2007), where we upheld the prejudgment interest awarded to the plaintiffs in that case. In Stevens, security company technicians brought a class action to recover overtime compensation for the drive times spent commuting to the first and last jobsites, for which the technicians had neither kept *128time records nor been paid. At trial, an expert calculated the drive times using a software program called “Map-point.” Brink’s contended that this data was insufficient to constitute a liquidated claim entitled to prejudgment interest because it required the jury to rely on opinion or discretion. We disagreed and concluded that prejudgment interest is appropriate where the evidence furnishes objective data that, if believed, makes it possible to compute the amount owed with exactness. We held that the technicians’ damages were liquidated and subject to prejudgment interest, reasoning that the jury could believe the drive times calculated with Mappoint and use it along with the technicians’ actual wages to calculate damages. The same reasoning should apply here.
¶56 As in Stevens, the providers’ damages in this case were capable of being determined with exactness by using an hours worked times hourly rate calculation. Here, both parties used reliable mathematical calculations to determine the number of unpaid hours that the Department of Social and Health Services (DSHS) wrongfully withheld from the providers, much like the computer algorithm and statistical analysis used to calculate the hours that went unpaid in Stevens. Interestingly, at trial, DSHS acknowledged that the damages were capable of accurate calculation and seemed to dispute only how to calculate the damages, stating, “Neither side, neither party has questioned the ... reliability of the statistical analyses____That isn’t what the dispute is. The dispute is, how do you get to your particular numbers and which criteria do you use.” 14 Verbatim Report of Proceedings at 2779. Although DSHS now disputes the accuracy of the statistical analysis used by its own experts to calculate the hours that went unpaid, as we said in Stevens, this does not render the claim unliquidated. The jury could believe the expert testimony regarding the number of unpaid hours and use it along with the providers’ hourly rate in the contract to calculate damages. Therefore, no discretion or opinion was required to enable *129the jury to determine how much the providers should have been paid had the shared living rule not been in effect.
¶57 Although a claim is unliquidated if the fact finder must exercise discretion, Washington cases have stressed that the act of fact finding is distinct from the exercise of discretion. In Dautel v. Heritage Home Center, Inc., 89 Wn. App. 148, 948 P.2d 397 (1997), an employee filed a claim against her former employer for wages and commissions owed. Although the parties disputed the percentage to be applied to the employee’s unpaid commissions (the employee argued it should be 20 percent and the employer argued it should be 10 percent), the damage award was a liquidated sum because it “could be computed with exactness once the trial court determined that [the employee] was entitled to her full commission rate of 20 percent.” Dautel, 89 Wn. App. at 155. Similarly, in Egerer v. CSR West, LLC, 116 Wn. App. 645, 67 P.3d 1128 (2003), a landowner sued an excavation contractor for failing to deposit fill on the landowner’s property, as arranged under contract. Although both parties agreed that the measure of damages was the difference between the market price of fill and the contract price, the parties presented conflicting evidence of market price ranging from $1.10 to $46.80. The damages in that case were a liquidated sum because
[l]ike Dautel, where the trial court exercised discretion only to find the appropriate commission percentage, the trial court here exercised discretion only to find the appropriate market price. The amount . . . actually owed could be computed with exactness once the trial court found that $8.25 per cubic yard was the market price.
Egerer, 116 Wn. App. at 654. As in Dautel and Egerer, once the jury resolved the conflicting evidence over the number of hours eliminated by the shared living rule, damages could be computed with exactness.
¶58 By comparison, Washington cases establish that a claim is unliquidated where the amount claimed may not be *130arrived at by computation but instead requires the jury to make an award based on opinion or discretion. See Aker Verdal A/S v. Neil F. Lampson, Inc., 65 Wn. App. 177, 192, 828 P.2d 610 (1992) (claim for labor costs was unliquidated since “it was within the jury’s discretion to determine a reasonable hourly rate”); Maryhill Museum of Fine Arts v. Emil’s Concrete Constr. Co., 50 Wn. App. 895, 751 P.2d 866 (1988) (claim was unliquidated where a museum, which was damaged by water leaks, was unique and thus without a market value so that the measure of damages was left to the fact finder’s discretion); Ski Acres Dev. Co. v. Douglas G. Gorman, Inc., 8 Wn. App. 775, 508 P.2d 1381 (1973) (claim was unliquidated where the jury resolved the reasonableness of the cost of repairing damage to a building). In this case, the jury was not asked to determine the reasonableness of the hours that the provider class worked, the hourly rate paid, or the amount of damages. Rather, both parties presented the jury with damage calculations that were based on mathematical formulas specified in the contract and DSHS’s own regulations. The trial judge properly concluded that the claim was a liquidated sum.
¶59 The lead opinion concludes that prejudgment interest is not proper here because the damage calculations required individualized data that DSHS did not collect during the period of the shared living rule and therefore the calculations were not exact, but “only estimates.” Lead opinion at 125. But our state’s cases have never required complete certainty in order for a claim to be deemed liquidated. See McConnell v. Mothers Work, Inc., 131 Wn. App. 525, 536, 128 P.3d 128 (2006) (damages were liquidated even though experts for both sides testified that an exact computation of overtime hours worked by the managers was impossible). In Stevens, the drive times were not documented or calculated during the period at issue yet we still upheld the award of prejudgment interest. And the drive times calculated by the computer software in that case were “only estimates” because the exact drive times may *131have been longer or shorter due to traffic volumes, inclement weather, or variable driving speeds of each technician.
¶60 Moreover, as we previously noted, “ ‘It may be safely said that the tendency has been in favor of allowing interest rather than against it, and that the degree of certainty or ease with which the approximate amount can be ascertained has grown less and less stringent.’ ” Prier, 74 Wn.2d at 34 (internal quotation marks omitted) (quoting 5 Arthur Linton Corbin, Corbin on Contracts § 1046 n.69, at 280 (1964)). “Washington courts generally favor prejudgment interest based on the premise that a party that retains money it should have paid to another should be charged interest.” Pierce County v. State, 144 Wn. App. 783, 855, 185 P.3d 594 (2008). It “compels a party that wrongfully holds money to disgorge the benefit.” Mahler v. Szucs, 135 Wn.2d 398, 430, 957 P.2d 632 (1998).
¶61 Although the jury found DSHS’s expert witnesses persuasive and ultimately adopted a number within its range of damage calculations, DSHS now contends that the damages could not have been calculated with certainty prior to the entry of judgment. But DSHS has always been able to calculate the amount it owed based on the contract formula. In fact, the hours and corresponding lost wages leading to the jury’s verdict were calculated and based upon DSHS’s own regulations and data, statistical analysis, and wage and benefit information in the collective bargaining agreements.3 The trial court’s decision to award prejudgment interest on the contract damages properly compels DSHS to disgorge this benefit and compensates plaintiffs for the delay in receiving the funds due to them. For these reasons, I would affirm the trial court in all respects.
Although the amount of damages awarded to the providers is substantial, part of that is because DSHS chose to continue applying the shared living rule for years after the first trial court held it to be invalid. The complexity in this case was perhaps caused by the State’s delay in continuing to apply the shared living rule after invalidation.