There are other variations of that quote about five computers: e.g. the UK would only need that kind of number.
For the publicly known computations of that time - gunnery trajectories etc., that number is perhaps right. But I believe over a dozen instances of Colossus were built for code cracking. So even then the estimate of five was way out.
However the real expansion of computing came with data processing, where record keeping outweighed the relatively small amount of computation. IBM should have known that, given their existing business in accounting machines fed with punched cards.
Biting the hand that feeds IT
