Cases applying the some loss = duty to assess/Chaplin v Hicks/best estimate rule
Figures in brackets are a reference to paragraph numbers in The Law of Damages

Davies J at 618: "...it seems to me to be clearly laid down there by the learned Judges [in Chaplin v Hicks] that such an impossibility [of assessing damages with certainty/mathematical accuracy] cannot "relieve the wrongdoer of the necessity of paying damages for his breach of contract" and that on the other hand the tribunal to estimate them whether jury or Judge must under such circumstances do "the best it can" and its conclusion will not be set aside even if "the amount of the verdict is a matter of guess work."" (Emphasis added by Spence J in Penvidic Contracting Co. Ltd. v. International Nickel Co. of Canada Ltd (1975) 53 DLR (3d) 748 (6.14)).

[Note that a guesstimate which is wholly erroneous/clearly wrong as to quantum (clearly not the amount, on balance of probabilities, suffered as a result of the breach) would be overturned on appeal]

Mason CJ and Dawson J: "31. The settled rule, both here and in England, is that mere difficulty in estimating damages does not relieve a court from the responsibility of estimating them as best it can: Fink v. Fink (1946) 74 CLR 127, at p 143; McRae v. Commonwealth Disposals Commission (1951) 84 CLR 377, at pp 411-412; Chaplin v. Hicks (1911) 2 KB 786, at p 792. Indeed, in Jones v. Schiffmann (1971) 124 CLR 303, Menzies J. went so far as to say that the "assessment of damages ... does sometimes, of necessity involve what is guess work rather than estimation": at p 308. Where precise evidence is not available the court must do the best it can: Biggin and Co. Ltd. v. Permanite Ltd (1951) 1 KB 422, per Devlin J. at p 438. And uncertainty as to the profits to be derived from a business by reason of contingencies is not a reason for a court refusing to assess damages: see McGregor on Damages, 15th ed. (1988), pars 357-359."

Dean J (applied in Lakatoi Universal Pty Ltd v L.A. Walker; Ensile Pty Ltd v Walker Consolidated Investments [2000] NSWSC 113 at 1394): "125. In Fink v. Fink (1946) 74 CLR 127, at p 143, Dixon and McTiernan JJ. said: "Where there has been an actual loss of some sort, the common law does not permit difficulties of estimating the loss in money to defeat the only remedy it provided for breach of contract, an award of damages."

Edmund Davies LJ: "Regrettably vague though the evidence is, my conclusion is that it points not only to a decrease in profitability since 1965 [ie, inference of some harm], but also to that decrease being due to the accident. My greatest difficulty is in quantifying the loss. ...[A nil award] is a conclusion to which I have been frankly loth to arrive..... Doing the best I can [applying the best estimate rule], and fully realising that I too am rendering myself liable to be attacked for simply �plucking a figure from the air�, I think the proper compensation under this head is �2,500."

Missing evidence as to the value of a secondhand photocopier - Hirst LJ: "Mr Mayall says that the judge was wrong to pluck a figure out of the air and that, as the plaintiffs could not prove a concrete percentage for the discount for a secondhand machine as compared to a new one, they should be allowed nothing at all. It goes without saying that this would militate strongly against any concept of justice, since Mr Mayall himself inevitably accepts that the secondhand machine must have been worth significantly less than a brand new one."

At 1^st instance in the Alger case Diamond J said: "What am I to do? I cannot ignore it ....the machine must have had some value...... I have come to the conclusion, doing the best I can, however, that I should put a value on this photocopier rather than to disallow the claim in toto."

Hughes CJ: "The court would not deny �the one fact that stands undoubted,� [ie that some of the net profit was attributable to the copyright infringement] and, making the best estimate it could, it fixed petitioners� share at one-fifth of the net profits, considering that to be a figure �which will favor the plaintiffs in every reasonable chance of error.�"

Mustill J: "In strict logic, the plaintiff should fail for want of proof that the breach has caused the [specific amount of] damage. Yet this seems too strict, for the plaintiff has proved some loss;.. ...I see no reason why the present impossibility of making a precise apportionment of impairment and disability in terms of time, should in justice lead to the result that the defendants are adjudged liable to pay in full, when it is known that only part of the damage was their fault. What justice does demand, to my mind, is that the court should make the best estimate which it can, in the light of the evidence."

Leonard J: "Being satisfied that Shimizu did suffer some disruption to the Tower, in particular delay to the construction of SD2 [stair drum 2], but that it ceased, or should have ceased, to have effect by L6, the Arbitrator was under a duty to assess quantum. He declined to do so on the basis that calculations were lacking. He could have either found a figure, doing his best on the material available or invited the further assistance [considered under missing evidence] of the parties. Having found a right he could not deny a remedy�."

"[30] Where there are variables involved, as usually occurs in assessments of business profits or losses, if precise figures had to be proved few plaintiffs could succeed. Where, as here, it is established that a particular factor was causative but its precise contribution to the loss could not be correctly calculated in precise dollar terms, a more robust approach is required of the courts. It is not a matter of whether an expert could give a reasoned assessment and could defend the number he or she came up with. As Lord Mustill said in Smith New Court Securities Ltd v Scrimgeour Vickers (Asset Management) Ltd at p269, "the assessment of damages often involves so many unquantifiable contingencies and unverifiable assumptions that in many cases realism demands a rough and ready approach to the facts". Speaking more formally in Tai Hing Cotton Mill Ltd v Kamsing Knitting Factory [1979] AC 91, the Privy Council concluded, at p106, that "the ends of justice would be best served if they [Their Lordships] were to fix a new figure of damages, as best they can upon the available evidence, such as it is".

[31] To the same effect, in Walsh v Kerr [1989] 1 NZLR 490, 494, this court noted that "There are cases where, although the assessment can only be largely speculative and the evidence is exiguous, the Court will do the best it can to arrive at a figure if satisfied that there has been some real damage".See, also, Ellmers v Brown (1990) 1 NZ Conv C 190,568 at 190,579."

"[933] This principle [ie Chaplin v Hicks/Penvidic/Wood v GVR/best estimate rule] is frequently applied in construction cases by British Columbia Courts: TNL Paving Ltd. v. British Columbia (Ministry of Transportion and Highways) (1999), 46 C.L.R. (2d) 165 (B.C.S.C.) at p. 284; British Columbia Hydro & Power Authority v. Canada (Minister of Public Works and Government Services), [1996] B.C.J. (Q.L.) No. 2131 (B.C.S.C.) at p. 7; and British Columbia Hydro & Power Authority v. Marathon Realty Co. (1992), 89 D.L.R. (4th) 419 (B.C.C.A.) at pp. 424-5.

[934] It is common in construction cases for trial judges to be called upon to:

(a) allocate responsibility for the cost overruns on a project between the plaintiff and the defendant in rough percentages based upon the totality of the evidence, without having been provided with a detailed breakdown of the overrun: TNL, supra, at pp. 283 and 287 (where the Court assessed damages at $1,250,000.00, based on a total cost overrun of $1,924,000.00 and a conclusion that the plaintiff had contributed to some unquantified extent to its losses); Opron Construction Co. v. Alberta (1994), 14 C.L.R. (2d) 97 (Alta. Q.B.) at pp. 298-9.

(b) determine the approximate percentage of the total delays on a project which were caused by the defendant's conduct:TNL, supra at p. 287 and Foundation Co. of Canada v. United Grain Growers Ltd. (1997), 34 B.C.L.R. (3d) 92 (B.C.C.A.) at p. 101;

(c) allocate fault for a particular loss between the plaintiff and the defendant: B.G. Checo, supra, at p. 9-10 (50% of a claim was held to be recoverable based on a witness's evidence that "he would say half" of a particular delay was caused by the claimable event as opposed to other delays.)

[935] In Opron, supra, Feehan, J. concluded that:

To put a figure on each of these causes of loss is impossible. Any attempt to calculate the plaintiff's claimable loss is so fraught with pitfalls that I would be foolish to attempt it. Small things and minor decisions become major elements. There are so many contingencies that no matter how often I attack the problem, the final figures vary. I cannot put an exact figure on how much the plaintiff harmed itself with bid errors, unbalancing the bid, errors in production, errors in supervision, errors in labour and equipment utilizations, errors in scheduling, errors in subcontracting, errors relating to the plaintiff's misrepresentation of the weather conditions, as well as many other actions or lack thereof which caused the plaintiff to lose money. I know that Opron's claimable loss is under one million dollars ($1,000,000). I know that it is somewhere above $750,000. I know that I will have to use round figures and approximates. I set Opron's claimable loss at $875,000.00. (at para. 923)"