From A stock market or equity market is a public entity (a loose network of economic transactions, not a physical facility or discrete entity) for the trading of company stock (shares) and derivatives at an agreed price; these are securities listed on a stock exchange as well as those only traded privately. ~ The size of the world stock market was estimated at about $36.6 trillion at the beginning of October 2008.[1] The total world derivatives market has been estimated at about $791 trillion face or nominal value,[2] 11 times the size of the entire world economy.[3] The value of the derivatives market, because it is stated in terms of notional values, cannot be directly compared to a stock or a fixed income security, which traditionally refers to an actual value. Moreover, the vast majority of derivatives 'cancel' each other out (i.e., a derivative 'bet' on an event occurring is offset by a comparable derivative 'bet' on the event not occurring). Many such relatively illiquid securities are valued as marked to model, rather than an actual market price.
This is a very nice, easy-to-follow book on the rolling stock strategy. Rolling stocks are stocks that roll up and down within a price range. You buy low, sell high, then repeat. I like this theory very much, although I have found it difficult to locate low priced rollers in negative markets. But of all strategies that I've seen, this is probably my favorite. The market right now is just so volatile that even when the indications appear to be in an up-trend buy mode, the least bad news anywhere in the market causes it to tank. Highly recommend.