In March 2001, Richard Notebaert, the chief executive officer of Tellabs, Inc., assured investors the growth of its best-selling product was solid.

Three months later, Notebaert told investors that the sharp drop in sales projections the Illinois-based telecommunications company experienced from January to June was due in large part to declining demand for that best-selling product, the Titan 5500.

In the meantime, stock prices fell to just under $16 per share from a high of $67.

In his assessment of the future performance of Tellabs’ best-selling product, Tellabs’ CEO was clearly wrong.

The question is: When did he know this?

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