"The best performing pension could produce more than three times more pension income than the worst performing one. The really bad news is that your pension fund is more likely to be amongst the bad than the good" The Observer
There are a number of ways of formulating an investment portfolio which has a realistic chance of producing attractive investment returns whilst restricting risk to a level acceptable to the investor.
It is important to recognise, quantify and use the risk profile of different asset classes, sectors and investment funds. These must then be considered in the context of the projected investment returns from each option. Finally (though there are of course many other stages in the process) preferred investment options should then be combined in such a way as to maintain investment returns from the overall portfolio whilst further restricting risk.
The answer (tailored for each individual investor)?