rosa sobrino explains. >> reporter: major stake holders who testified at a recent senate hearing on high frequency trading took conflicting positions on the issue. >> it is one where with increased disclosure and increased transparency everyone knows just how the game works but right now a lot of it is opaque. >> today our equity markets are the most liquid, transparent, efficient and competitive in the world. >> reporter: what is the problem with high frequency trading? some say it might enable predatory trading. imagine investors who try to make a large one-time purchase of a certain stock. to keep the purchase price low the investors buy through a broker that purchases the stock via several different stock exchanges and trading venues. but the purchases are not completed at the same time. the first purchase alerts predatory hft traders who have high-speed computer servers and systems. they can figure out the demand and in a fraction of a second can corner the market. as a result the price of the stock goes up and the investors must spend more money to complete their purchase. a japane