The stock exchanges are highly psychologically driven and the media can influence the exchange rates to a large extent.
As an example:
The news came from the fact that the Chinese stock exchange would issue more bitcoin adjustments and the bitcoin price fell by as much as 50% because people were afraid that the bitcoin price could swiftly fall and could fall as many decided to sell their bitcoin fast and the bitcoin price fell sharply afterwards. On the other hand, many noticed that the bitcoin price was very low and that it had been much higher before. It was time to buy bitcoins at a lower price and the bitcoin price set a new record in a very short time. Then consider the opportunity to keep track of the most important news sources, as they greatly affect the psychological flow, and thus the prices.
Coinbase has announced that they will accept BTC (Bitcoin Cash) in its stock exchange at the end of 2017 and this is good news because it means that BCH will be accepted in exchange for a major stock exchange and that you will also be able to exchange BTC (Bitcoin Cash) to real money such as Norwegian kroner.
Consequently, people in public space understood that the use of BCH is going to increase, so the price began to rise, people began to buy BCH in advance.
What happened on the stock exchange? BCH doubled during the week. Think of one thing ... If you are publisher of this post before posting such a message online, purchase a large amount of BCH and then publish the message, what will your own benefit be?
The conclusion is that those who get all the information about such changes in advance can predict the future to a certain extent, and buy BCH at a lower price and sell at a higher price afterwards.