In April 2018 I originally made a prediction that the stock market would drop significantly by July 2019.  I pulled the forcast portion from the article in Oct 2019.  This is the original article.  I think the significant drop we have seen over the last couple of weeks is because of a stock bubble caused by high deficits (during economic prosperity) and not because of the popularity of index funds.  If however, stock prices go down another 10%, I think economist will start to examine, and probably verify, my theory that too many people have been using index funds as their investment strategy.