2014-32 Stock market as ebola

Stock markets fell last week (Here is TSX, you can compare it with US stock indices by clicking "compare" at the top of the graph).
How to explain this?
In 2013 Nobel prize winner in economics, Robert Schiller, received the prize for "empirical analysis of stock prizes". He explains why shares sometimes fall for no apparent reason in this article
His explanation:
- short-term variations in stock prices are extremely hard to predict
- but we should try because "we live in the present"
In his view stock prices are sometimes moved by "thought viruses" and spread by contagion, just as biological viruses.
The virus this time: well, there are three

1. global slowdown
2. deflation
3. and the big one: secular stagnation

People are concerned that the world economy entered a new phase of slow growth. In this context secular means "lasting a very long time". So this sounds serious. If there is an economic slowdown which lasts a long time, profit expectations fall, future dividends will be lower and so stocks are overpriced.

Once a lot of people get the thought virus and start selling stocks, the forecast of falling stock prices becomes self-fulfilling. Stock prices fall, people become even more concerned, sell more stocks and stocks fall further.