The mathematical description of stock market movements has been a subject of intense interest. The conventional assumption has been that stock markets behave according to a random log-normal distribution.[9] Among others, mathematician Benoît Mandelbrot suggested as early as 1963 that the statistics prove this assumption incorrect.[10] Mandelbrot observed that large movements in prices (i.e. crashes) are much more common than would be predicted from a log-normal distribution. Mandelbrot and others suggested that the nature of market moves is generally much better explained using non-linear analysis and concepts of chaos theory.[11] This has been expressed in non-mathematical terms by George Soros in his discussions of what he calls reflexivity of markets and their non-linear movement.[12] George Soros said in late October 1987, 'Mr. Robert Prechter's reversal proved to be the crack that started the avalanche'.[13][14]
But Ethan Harris, head of global economics at Bank of America Merrill Lynch, lists a number of global disputes coming to a head this fall, including tariffs on imports from China, the potential for auto tariffs on other countries, Iran oil sanctions kicking in, Congress facing another budget deadline and the election in November. "The risk calendar gets quite big this fall," he said. "September is part of it, but it's really the whole fall period."
From October 6–10 the Dow Jones Industrial Average (DJIA) closed lower in all five sessions. Volume levels were record-breaking. The DJIA fell over 1,874 points, or 18%, in its worst weekly decline ever on both a points and percentage basis. The S&P 500 fell more than 20%.[36] The week also set 3 top ten NYSE Group Volume Records with October 8 at #5, October 9 at #10, and October 10 at #1.[37]
Any of the measurements people quote—any of the stock market indexes which go up and down—are just measurements. They're averages. They're big bundles of numbers all mixed together. In all truth, they only reflect a snapshot of a point in time. They're numbers that stocks happened to end on when trading stopped for the day (or, at least, paused until after hours trading took over).
"Panic is already starting to set in, which is kind of incredible when you actually think about it," said Michael Yoshikami, CEO of Destination Wealth Management. "The S&P is trading where it was in sometime in December. So it's not like we're retracing an entire 12 months of returns here. I think investors are just understandably nervous. It probably is programmed trading kicking in at this point."
Fast forward thirty years. I’ve discovered an analog chart model that correlates the markets of the 1980s to the markets of the 2010s. Specifically, it correlates the S&P 500 from 1978 to 1987 to the S&P 500 from 2010 to 2018. The correlation rate? 94%. In other words, this model shows that the stock market of the past eight years is trading similar to the stock market of the 1980s.
This year’s rate rises however are a bit alarming as this graphic shows — 70% in the last year. When you consider that such rises always accompany recessions, it’s no surprise to see a stock market correction or pullback and even a housing market slide. To investors, this scenario doesn’t look good. It can affect stock prices and discourage investment in new US businesses.
Trying to time a market crash or correction is pretty much impossible, and trying to estimate how much will be lost in that crash is even more difficult. If you had listened to David Haggith’s  doom and gloom warnings back in 2012, you would have missed out on one of the greatest bull runs in history. You also have to realise that permabear “experts” such as Marc Faber exist and that they will constantly make predictions about how the next big market crash is just seconds away. To sum it up: Nobody really knows when it’s going to happen or if it’s worth staying on the sidelines while the market continues to grow upwards. Well, everyone except me of course. I’m 100% certain that a market crash is going to happen in 2018.