After such a long run of strong market returns, it is only natural that investors' attention starts to move toward when that run might end, and as each day passes, we move closer to the end of the cycle.

A key question we hear posed more and more frequently is whether investors should be significantly adjusting their portfolios or whether they should delay investing new money. This sentiment essentially represents a desire to attempt to pick the peak in the market.

We can turn to history in order to try and respond to such questions. We look at past market conditions and establish what investors may need to do if they are to effectively time the market and end up with a superior result to a buy-and-hold investor. We find that there is a very narrow window of time to make the market exit and re-entry call, suggesting that market timing, while not impossible, is very difficult.