Adam Smith (1723 - 1790) in "The Money Game" wrote: "Prices have no memory and yesterday has nothing to do with tomorrow. Every day starts out fifty-fifty!"
If the above statement is to be trusted, then you could just take the 50 - 50 odds, expand their daily time horizon to a yearly one, and decide whether or not to "stay in the stock market game" in the next year!
Decide on just a flip of a coin?
Given the past year's returns, what does this "flip" imply for the investors' chances this coming year?
Well, that is a matter of asking the question the right way!
If you assume that the years are flipping randomly, and that there is no bias for any year, then you could ask if it is fair enough to assume that flipping through a calendar is otherwise the same as just flipping a coin?
Let's assume that you were just flipping a coin. Then, YES ...
The odds of one flip would always be 50 - 50!
Indeed, you might be led to start questioning about how fair the coin actually would be! In this case, you really should look back and base your expectations on historical econometric analysis and try to establish how fair the coin would be!
But if you are guessing that some things do look like a flip of a coin, shouldn't you also assume that just because i.e. we had a negative year, we're now going to get a positive one?
Who knows ... Investments based on that kind of speculation might actually end up yielding a positive result!
But the odds are still only 50 - 50!
On the other hand ...
I do know that ...
I will get a much better than 50 - 50 chance!