Who sets the price and provides the quoted price values for stocks?
"The ""price"" is the price of the last transaction that actually took place. According to Motley Fool wiki: A stock price is determined by what was last paid for it. During market hours (usually weekdays from 9:30AM-4:00PM eastern), a heavily traded issue will see its price change several times per second. A stock's price is, for many purposes, considered unchanged outside of market hours. Roughly speaking, a transaction is executed when an offer to buy matches an offer to sell. These offers are listed in the Order Book for a stock (Example: GOOG at Yahoo Finance).  This is actively updated during trading hours. This lists all the currently active buy (""bid"") and sell (""ask"") orders for a stock, and looks like this:  You'll notice that the stock price (again, the last sale price) will (usually*) be between the highest bid and the lowest ask price. * Exception: When all the buy or sell prices have moved down or up, but no trades have executed yet."
The strategy has intrinsic value, which may or may not be obstructed in practice by details mentioned in other answers (tax and other overheads, regulation, risk). John Bensin says that as a general principle, if a simple technical analysis is good then someone will have implemented it before you. That's fair, but we can do better than an existence proof for this particular case, we can point to who is doing approximately this. Market makers are already doing this with different numbers. They quote a buy price and a sell price on the same stock, so they are already buying low and selling high with a small margin. If your strategy works in practice, that means you can make low-risk money from short-term volatility that they're missing out on, by setting your margin at approximately the daily price variation instead of the current bid-offer spread. But market makers choose their own bid-offer spread, and they choose it because they think it's the best margin to make low-risk money in the long run. So you'd be relying that: "In this instance ""quotational"" is a reference to a market price quote, not a mathematical function.  Staunch ""value investors"" like Graham, Dodd, Munger, Buffett et al. believe there is a material difference between what security is ""worth"" and what the current market mood quotes as its price.   You, the investor, perform your analysis then derive a value for a security. If there has been no material change to an aspect of the security you analyzed then there hasn't been a change in that security's value, even if there has been a decline in the price quoted by the market, that is a ""quotational loss.""" The values of 12, 26 and 9 are the typical industry standard setting used with the MACD, however other values can be substituted depending on your trading style and goals. The 26d EMA is considered the long moving average when in this case it is compared to the shorter 12d EMA. If you used a 5d EMA and a 10d EMA then the 10d EMA would be considered the long MA. It is based on what you are comparing it with. Apart from providing signals for a reversal in trend, MACD can also be used as an early indication to a possible end to a trend. What you look out for is divergence between the price and the MACD. See chart below of an example:  Here I have used 10d & 3d EMAs and 1 for the signal (as I did not want the signal to show up). I am simply using the MACD as a momentum indicator - which work by providing higher highs in the MACD with higher highs in price. This shows that the momentum in the trend is good so the trend should continue. However the last high in price is not met with a higher high in the MACD. The green lines demonstrate bearish divergence between price and the MACD, which is an indication that the momentum of the trend is slowing down. This could provide forewarning that the trend may be about to end and to take caution - i.e. not a good time to be buying this stock or if you already own it you may want to tighten up your stop loss. "Who are the losers going to be? If you can tell me for certain which firms will do worst in a bear market and can time it so that this information is not already priced into the market then you can make money. If not don't try. In a bull market stocks tend to act ""normally"" with established patterns such as correlations acting as expected and stocks more or less pricing to their fundamentals. In a bear market fear tends to overrule all of those things. You get large drops on relatively minor bad news and modest rallies on even the best news which results in stocks being undervalued against their fundamentals. In the crash itself it is quite easy to make money shorting. In an environment where stocks are undervalued, such as a bear market, you run the risk that your short, no matter how sure you are that the stock will fall, is seen as being undervalued and will rise. In fact your selling of a ""losing"" stock might cause it to hit levels where value investors already have limits set. This could bring a LOT of buyers into the market. Due to the fact that correlations break down creating portfolios with the correct risk level, which is what funds are required to do not only by their contracts but also by law to an extent, is extremely difficult. Risk management (keeping all kinds to within certain bounds) is one of the most difficult parts of a manager's job and is even difficult in abnormal market conditions. In the long run (definitions may vary) stock prices in general go up (for those companies who aren't bankrupted at least) so shorting in a bear market is not a long term strategy either and will not produce long term returns on capital. In addition to this risk you run the risk that your counterparty (such as Lehman brothers?) will file for bankruptcy and you won't be able to cover the position before the lender wants you to repay their stock to them landing you in even more problems." "I expect that data may be copyright. Data that's published (e.g. on a newsfeed or web site) is subject to terms of use. Standard & Poor's web site says, about the Shiller indexes, Who do I contact at S&P to license my   use of these indices?   Questions   regarding licensing the   S&P/Case-Shiller Home Price Indices   can be addressed to:  Bo Chung    Managing Director    bo_chung@standardandpoors.com,   +1.212.438.3519 As for 'recording' the information yourself, that may depend on how and where (e.g. from what source) you're recording it. If for example you tried to record prices from the Canadian MLS (Realtor's) network, they too have their own terms of use on the data they publish. Copyright laws vary from country to country (and terms of use certainly vary): for example see http://en.wikipedia.org/wiki/Feist_v._Rural which is case law about copyrighting a phone directory in the USA, and contrast that with http://en.wikipedia.org/wiki/Database_right which is European legislation. So who owns data if it is determined by free market? I guess that ""determined by free market"" means that buyers and sellers are publishing their offers-to-buy and their offers-to-sell, and I guess that the publisher (e.g. the stock exchange) has 'terms of use' about the data (the offers) that they're publishing." "As others have noted, your definition of ""market price"" is a bit loose.  Really whatever price you get becomes the current market price.  What you usually get quoted are the current best bid and ask with the last transaction price.  For stocks that don't trade much, the last transaction price may not be representative of the current market value. Your question included regulation (""standards bureau""), and I don't think the current answers are addressing that.  In the US, the Securities and Exchange Commission (SEC) provides some regulation regarding execution price.  It goes by the designation Regulation NMS, and, very roughly, it says that each transaction has to take the best available price at the time that it is executed.  There are some subtleties, but that's the gist of it. No regulation ensures that there will be a counterparty to any transaction that you want to make.  It could happen, for example, that you have shares of some company that you're never able to sell because no one wants them. (BitCoin is the same in this regard.  There is a currently a market for BitCoin, but there's no regulation that ensures there will be a market for it tomorrow.) Outside of the US, I don't know what regulation, if any, exists." The quote price is simply the last price at which a trade completed. "This functionality is widely available, not only on brokerage sites, but also financial management and even financial information sites.  For instance, two of the latter are Google Finance and Yahoo Finance.  If you are logged in, they let you create ""portfolios"" listing your stocks and, optionally, the size of your holdings in that stock (which you don't need if you are just ""watching"" a stock).  Then you can visit the site at any time and see the current valuations."