Over the period of Jan 2001 through July 31, Lay made approximately 360 (yeah - three hundred sixty) trades in Enron stock. It was like he was day-trading in his own company! Then suddenly on August 1st, the trade flurry stopped -- a couple more trades on Aug. 20-21, and that was the end of the list (there's a delay before listings are made, so one can't be certain of trades after October, but clearly something happened to slow the tide of trades after July).
So it's pretty obvious that something wierd was going on -- that's a crazy amount of trading. It's really to the point at which one would have to question whether the CEO/Chairman of the Board was paying any attention to his primary job... but certainly he knew (above anyone) exactly where the stock price stood -- probably on an hourly basis!
And, unfortunately for the other investors, those insider trades are reported monthly.