Economist and former Clinton deputy assistant secretary of the U.S. Treasury Brad Delong asks, “Is the Federal Reserve too volatile and hair-trigger? Or is the ECB too sluggish?“
I think that a more accurate answer is that Alan “Bubbles” Greenspan is an idiot, you will notice that the volitility, except for the steep decline at the end, is all under his watch, and “Helicopter Ben” throwing money out the window is as a result of Greenspan’s disastrous policies.
I would also note that the ECB is not charged with maintaining employment, just keeping inflation down, so they would naturally be slower to reduce rates. They have no balance to keep for them.