Despite a rally in equities, investor confidence still fell in the U.S. and Europe in September, according to research by State Street Global Markets.

The data from its monthly Investor Confidence Index shows that globally, investor confidence fell four points from 92 to 88, from August to September.

The drop was most pronounced in North America where confidence ratings fell 7.3 points from 95.2 to 87.9. Asian investors bucked the trend, however, and their confidence rose 4.4 points from 103.5 to 107.9.

“This month’s decline in global investor confidence is somewhat surprising, in light of the meaningful rally in risky assets since the last data release,” said Harvard University professor Ken Froot, who helped create the index.

“Looking at the numbers more closely, however, we see that the decline is driven largely by North American investors. Elsewhere, we see a much more upbeat mood. One underlying driver here is the persistent softness observed in the U.S. economy over the summer, which contrasts with the resilience of markets elsewhere such as Australia, Canada, New Zealand and Sweden.”

The index measures investor confidence on a quantitative basis by analyzing the actual buying and selling patterns of institutional investors.