This is actually true in most cases. The entire Wall Street tends to make money. That is why the stock exchange (NASDAQ, NIKKEI, etc.) indexes keep going up and up, with the sole exception of a GFC or the like.
It is individual stocks and investments that might lose you money.
The Civ4 NW is not a single investment
Hence, diversify your shares portfolio!
I don't want to hijack the thread, but measuring whether Wall St makes or looses cash is actually very difficult, and depends on how long you choose as a measurement period. By some measurements you'd be better putting your money in the bank for 10 years than into any stock market.
But yes, diversify your portfolio...