The speech which triggered a near universal rise in equities markets around the world on Tuesday evening and Wednesday morning was not even an official Federal Reserve event.
It was a well-established and highly regarded event that Yellen spoke at, but it was not one of the FOMC meetings which have the official role of setting monetary policy and providing guidance on its future direction.
The devil is not in the detail
The detail of what Yellen said was also much less precise than the sort of things Draghi and Kuroda have said recently. She simply implied that the next 25 basis point rise may be a little further off than many had anticipated. The ECB and Bank of Japan chiefs on the other hand have been in the practice of announcing tens of billions in new QE when they get to their feet to deliver speeches.
For anybody questioning the power of central bankers in light of recent events the Federal Reserve chair and the reaction to her words shows that not all central bankers are equal. It is not necessarily what is being said that matters most to investors, but who is saying it.