5 The observations of Lord Woolf at 724-726 are to similar effect. So also are the observations of Lord Denning MR in Wallersteiner v Moir (No 2) [1975] QB 373 at 388 and the observations of the late Dr F A Mann in an article entitled "On Interest, Compound Interest & Damages" in (1985) 101 LQR 30.
6 A comprehensive analysis of the arguments in favour of compound interest is contained in a report of the United Kingdom Law Commission entitled "Pre-Judgment Interest on Debts & Damages": Report Law Com No 287, 24 February 2004. The authors stated that the obvious reason for awarding compound interest is that it reflects economic reality. They added that simple interest can never be relied upon to produce a just indemnity for the loss occasioned by delay in payment.
7 At a general level, and as a matter of principle, the many statements in favour of compound interest are truisms. This explains why in Canada, the Law Reform Commission of British Columbia stated in 1987 that pre-judgment interest should be mandatory and should be compounded monthly: LRC 90. It also explains why in 1994, the New Zealand Law Commission published Report No 28 stating that with few exceptions, there should be mandatory compound interest on all judgments for money claims and that the compounding should be monthly.
8 However, it should be recognised that in any particular case, depending on the rate adopted, or the period of calculation, simple interest may operate fairly. Of course, the disadvantage of simple interest will be magnified the longer the period of calculation. But that disadvantage may be offset if the simple interest rate is set at a high level. An arithmetical graph can be constructed readily to demonstrate, for example, that over a five year period, 7% compound interest will produce the same result as 8% simple interest. On the other hand, over 10 years, the differential will be significant. And of course the differential will increase exponentially: Report Law Com No 287 (supra), Appendix A.
9 This offsetting effect, by using a high rate for the calculation of simple interest, is exemplified by the policy approach taken in relation to the Late Payment of Commercial Debts (Interest) Act 1998 (UK). That Act provides that any qualifying debt carries only simple interest. The government's Green Paper recommended an interest rate of 4% above the base rate. It favoured simple rather than compound interest because it was said to be significantly easier to calculate and because the difference between compound and simple interest was thought to be immaterial in most cases. Following consultation, the government adopted the suggestion of the Bank of England and increased the proposed interest rate to 8% above the base rate. This higher rate was said to represent the rate of overdraft interest available to the smallest and most vulnerable businesses: Report Law Com No 287 (supra), paragraphs [2.25] and [2.26]. The evident purpose of the selection of a rate 8% above the base rate, was to ensure that a successful plaintiff received sufficient compensation, albeit on a simple interest basis.
Compound Interest - Equitable Principle
10 Quite independently of statute, equity has always adopted a broad approach to the award of interest. Equity courts have regularly awarded interest, including not only simple interest but also compound interest when justice demanded. This has included circumstances where money has been withheld or misapplied by a trustee or fiduciary: Hungerfords v Walker (supra) at 148. Lord Brandon made a statement to the same effect in President of India v La Pintada Compania Navigacion SA [1985] AC 104 at 116B. And in Wallersteiner v Moir (No 2) (supra), Lord Denning MR said at 388:
In addition, in equity interest is awarded whenever a wrongdoer deprives a company of money which it needs for use in its business … It may be that the company would have used it in its own trading operations; or that it would have used it to help its subsidiaries. Alternatively, it should be presumed that the wrongdoer made the most beneficial use of it. But, whichever it is, in order to give adequate compensation, the money should be replaced at interest with yearly rests, ie compound interest.
11 In 1978, the United Kingdom Law Commission described the equitable jurisdiction to award interest in broad terms: Law of Contract: Report on Interest (Law Com No 88). The authors stated:
21 The equitable jurisdiction to award interest and to fix the rate at which it should be paid is extensive … In such cases the court has an inherent power to order the payment of interest at whatever rate is equitable in the circumstances and may direct that such interest be compounded at appropriate intervals … Accordingly, we make no recommendations for change in relation to the equitable jurisdiction.