According to “ Fama & French Forum : “ Distributions of daily and monthly stock returns are rather symmetric about their means, but the tails are fatter (i.e., there are more outliers) than would be expected with normal distributions. (This topic takes up half of Eugene F. Fama's 1964 PhD thesis. Eugene Fama is 2013 Nobel laureate in economic sciences) In the old literature on this issue, the popular alternatives to the normal distributions were non-normal symmetric stable distributions (which are fat-tailed relative to the normal) and t-distributions with low degrees of freedom (which are also fat-tailed). The message for investors is: expect extreme returns, negative as well as positive. “ Did you see the patterns or characteristics in below charts ? Of course this is not the “patterns “ which I have described in separate blog under blog title of  “ Patterns , Patterns , Patterns ! “   Yes ! The stocks market return is not in the form of  “perfect normal ( aka Gaussian ) distribution “ ....