They go into the new decade with a spring in their step, after watching world stocks add over $25 trillion in value in the past 10 years and a bond rally put $13 trillion worth of bond yields below zero.

They also saw internet-based firms transform the way humans work, shop and relax. Now investors are positioning for the tech revolution's next 10 years.

Could we see a repeat of the roaring twenties, as the 1920s were known -- years of prosperity, technological innovation and such social developments as women winning the right to vote?

Possibly. But there's unease, along with all the euphoria. The current economic cycle is already the longest in U.S. history and a recession looks inevitable in the new decade -- which also will mark 100 years since the Wall Street crash of 1929.