516 trillion dollars

The Chinese tell it like it is:

"In 2007, the notional value of all outstanding derivatives contracts rose above 516 trillion U.S. dollars, which is about eight times global GDP."
http://english.people.com.cn/90001/90778/90858/90864/6544652.html

Investment banks targeted by "naked" shorting complained that the practice dilutes their shares and their market values evaporated.