This article is entirely devoid of content. It is completely worthless. Newsflash for everyone thinking about being involved with the markets: the reason they

This article is entirely devoid of content. It is completely worthless. Newsflash for everyone thinking about being involved with the markets: the reason they work is because there are participants with different motiviations and ideas on how to make money. Period. By definition, the "plankton" of the markets are the market makers (both designated and implied, read passive HFT). These guys provide immediacy. They do that with the express intent of continuously trying to manage their inventory of any particular stock to 0 (with constraints of their pricing model). This directly implies they have a very high turnover and a holding period that is minimized as much as possible. Why do they do this? Market makers provide a valuable service: immediacy. They supply to other traders an OPTION to trade with them by displaying liquidity on the standing limit order book. Therefore, they must deal with adverse selection (trading with counterparties who are more informed than they are). A market maker is there, ready to trade, and when someone lifts their offer or hits their bid they want to turn around and lay that position off as quickly as possible, ideally via another limit order being matched with a market order. This is the way they earn their living: by making the spread.