Article is from August 2007. Note the howling error on the last line. Just how many investors out there are ignorant of how money works? Margin cash could be taken as 110% of the money supply used to trade shares in the 2007 peak. Not "1.94 percent" as if there was cash to liquidate the entire NYSE market cap.
Even the discontinued super-broad M3 measure of money stood at only $10,366 Billion in March 2006. The corresponding NYSE Cap was $15,485 Billion, $5,119 Billion more, or 49.4% above the theoretical money supply. Let's leave aside the fact that the vast majority of that money wasn't "in broker accounts."