The markets aren't a zero sum game because neither stock markets nor the futures markets nor any others are a closed system. There is almost always a net inflow or outflow of cash to the "real" economy - everything from people with 401ks auto-allocating money to their retirement account every month out of their paycheck to some trader taking profits intraday and then cashing out so he can spend the profits (or depositing external funds to meet a margin call!)
From the thread: http://www.elitetrader.com/vb/newreply.php?s=&action=newreply&postid=1776388 Related answer (the question is at the bottom) is:
I am sorry but I find this thread excellent! "Long term investing in stocks is not." is valid only for major indices (which drop stocks and include new ones). If you include all stocks past and present, I am convinced that stocks are a NEGATIVE sum game if we restrict things to the general investor (meaning do not include investment bankers, pre-IPO investors, exchanges, brokers, and all those with zero risk positions).
So, for example, any trader who uses covered calls as part of his strategy to hedge is NOT a trader (as one example)....hmm. I think many would beg to differ. Many hedgers are traders. Every energy company that has hedgers who are traders who have a material affect on their P&L.