Back in my youth I did a course on philosophy and one of the books we read was Bertrand Russell’s The Problems of Philosophy. This is a quote from Chapter 6 – On Induction:
Domestic animals expect food when they see the person who feeds them. We know that all these rather crude expectations of uniformity are liable to be misleading. The man who has fed the chicken every day throughout its life at last wrings its neck instead, showing that more refined views as to the uniformity of nature would have been useful to the chicken.
Philosophical induction is of course a very different beast from mathematical induction. In our home town, Edinburgh University have created a programming language Haskell which can be proven correct by proof by mathematical induction. Mathematical induction is based on proofs rather than the slightly flimsy enumerative deduction in philosophy which is based on observation.
Going back to Russell he creates a severe problem for the Chartist. This is a very common investment mistake and I will admit that I have fallen for it myself in the past. It’s very easy to look at a graph for a stock and assume that this has some link to the future.
An individual example would be Enron which of course won many awards before collapsing to zero. A bigger example would be the pre-revolution Russian stockmarket which outperformed all of its competitors for a whole century before total wipeout. Both these examples are very negative but the failure of proof by induction also applies in the other direction. An obvious example would be Walmart which went for a few decades in a fairly flat way before completely taking off.
So next time you are looking at a graph and expect it to continue on its happy trajectory remember the story of Bertrand Russell’s chicken. The past is not a predictor of the future – good or bad.