It's been called the most hated bull run in history - the bears have been saying it can't last almost since it began. But is it, as some also say, the second longest in history?

Should investors be worried?

Talking to business editor at large Liam Dann on Market Watch, Pie Funds CEO Mike Taylor says a closer look at the performance of global share markets reveals it is not so clear cut.

It has been far from a straight run for share markets since 2009 with some markets dipping into bear territory in 2011 and early this year, he says.

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While there were some key economic drivers, like low interest rates, that looked likely to underpin the markets for some time no one coul predict the top.

So the key was to look for signs of "froth" or overexuberance in the market that suggest it is becoming detached from fundamentals, he says.