A key survey of German investor optimism fell in September for the ninth month in a row as the crisis in Ukraine, economic stagnation in Europe and the upcoming independence referendum in Scotland weighed on sentiment.

The ZEW institute said Tuesday its indicator of economic sentiment fell to 6.9 points from 8.6 points the month before. The index fell by less than expected; market analysts had foreseen a bigger drop to 5.0 points.

ZEW head Clemens Fuest said the downward trend "has slowed significantly." However, he said the economic climate is still characterized "by great uncertainty."

The index remains below its long-term average of 24.6 points.

It was based on a survey of 234 investment analysts conducted Sept. 1-15.