The financial services research group said their Global Investor Confidence Index increased by 8.7 points to 81.0 in April. North American investors helped push the figure with that sub index rising 8.0 points to 85.0.

Harvard University professor Ken Froot, who helps compile the report, called the jump "a significant move," although "not quite as big as the bounce seen after August 2007."

He also noted a "divergence in the timing of the cycle" as the "European confidence remained essentially flat," Froot said.

May results put the investor confidence index at 76.3 in Europe and 86.4 in Asia, State Street reported.