The compound interest calculations fail as a basis for a financial claim for several fundamental reasons.
First, the principal is undefined. Different calculations use different estimates of the value of enslaved labour, ranging across factors of ten or more. Some use the market price of enslaved people as the principal. Others use estimates of wages that would have been paid if the labour had been free. Others use the total value of goods produced. Each produces a radically different starting point, and the compounding effect means that differences in the principal become enormous over 200 years.
Second, the interest rate is chosen rather than derived. Different advocates use rates ranging from two percent to ten percent. Applied over two centuries, the difference between a two percent and a five percent rate produces results that differ by orders of magnitude. There is no principled basis for choosing one rate over another, because there is no actual debt instrument from which a rate could be read.
Third, compound interest only applies to actual debts between identifiable parties. It is a mechanism for calculating what one specific person or institution owes another specific person or institution when the terms of the debt are agreed. There is no agreed debt instrument, no agreed principal, no agreed rate, no agreed parties, and no agreed start date for the slavery reparations claim. Applying compound interest to these absent elements produces a mathematical output but not a financial claim.
Fourth, the resulting figures are so large as to be self-evidently unachievable, which suggests the calculation is being used for rhetorical rather than practical purposes. A claim of £200 trillion against Britain is not a serious financial demand. Britain’s entire GDP is approximately £2.5 trillion per year. The calculation would require eighty years of the entire British economic output. No advocate actually proposes this. The figures are cited to establish moral scale, not as a genuine demand. If so, they should be presented as rhetoric, not as calculation.
