A time traveller wants to get rich, so invests heavily in shares that were cheap in a time period he can reach, but he knows are going to get seriously profitable over the next few years. A typical example might be Apple circa 1995 - the price was usually around $1 to $2 from 1986 to 2004, then took off exponentially and is currently just under $350
Then he goes back to his own time, and discovers that the big rise never happened. Why? Because the investment caused a big enough blip in the share price that Steve Jobs decided to sell out, and the new owners never put the money into R&D that made Apple the giant that it is.
The idea here is that investment has always been risky, and there's a butterfly effect where pumping money into a company might change the conditions that made it successful.
Can anyone think of a story where this happens? And I'm not looking for the one where someone buys a few rare stamps and they suddenly aren't rare any more because the sudden demand means that more are printed!
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