What is the difference between predicting an election result and a stock movement?
Actually not that much, for both involve one fundamental ingredient that has always dogged the social sciences. Both involve an assessment of how large numbers of humans will behave at a given time. And unlike photons, humans do not rigidly follow strict laws of nature. They are in themselves very complex systems that are likely to change their views quite suddenly, be influenced by exogenous events or be plainly irrational.
This becomes particularly apparent when we come up to the results of an election as tight and fraught as the current U.S. presidential election. Trying to figure the end result becomes more akin to predicting short-term currency movements, which often seem somewhat random.
And just as with stocks, vast data are provided in elections, along with multiple methodologies for assessment of the data. The biggest volume of data is, of course, polls. But polls do not necessarily reflect how someone will ultimately behave when they are alone in that booth making their final voting decision, nor what factors can arise between the time of the poll and the actual vote. The selection of polling participants can also cause bias in results.
Then there are those who tell us they have systems. There is the "13 keys"-based analysis of U.S. history Professor Allan Lichtman, or the recent artificial intelligence system that predicted correctly the primaries and the last three presidential election results. Or there's the stock market itself. Going back to World War II, when the S&P 500 has declined between between July 31 and Oct. 31, a challenger has won the presidential election 86% of the time. The S&P 500 is down about 2.0% since its close on July 29.