Does a stock's price represent current liquidation of all shares?
"What if everyone decided to sell all the shares at a given moment, let's say when the stock is trading at $40? I imagine supply would outweigh demand and the stock would fall. Yes this is the case. Every large ""Sell"" order results in price going down and every large ""Buy"" order results in price going up. Hence typically when large orders are being executed, they are first negotiated outside for a price and then sold at the exchange. I am not talking about Ownership change event. If a company wants a change in ownership, the buyer would be ready to pay a premium over the market price to get controlling stake." "What if everyone decided to sell all the shares at a given moment, let's say when the stock is trading at $40? It would fall to the lowest bid price, which could be $0.01 if someone had that bid in place. Here is an example which I happened to find online:  Notice there are orders to buy at half the market price and lower... probably all the way down to pennies.  If there were enough selling activity to fill all of those bids you see, then the market price would be the lowest bid on the screen.  Alternatively, the bid orders could be pulled (cancelled), which would also let the price free-fall to the lowest bid even if there were few actual sellers. Bid-stuffing is what HFT (high frequency trading) algorithms sometimes do, which some say caused the Flash Crash of May 2010.  The computers ""stuff"" bids into the order book, making it look like there is demand in order to trigger a market reaction, then they pull the bids to make the market fall.  This sort of thing happens all the time and Nanex documents it http://www.nanex.net/FlashCrash/OngoingResearch.html Quote stuffing defined: http://www.investopedia.com/terms/q/quote-stuffing.asp I remember the day of the Flash Crash very well.  I found this video on youtube of CNBC at that time.  Watch from the 5:00 min mark on the video as Jim Crammer talks about PG easily not being worth the price of the market at that time.  He said ""Who cares?"", ""Its not a real price"", ""$49.25 bid for 50,000 shares if I were at my hedge fund.""  http://www.youtube.com/watch?v=86g4_w4j3jU You can value a stock how you want, but its only actually worth what someone will give you for it. More examples: Anadarko Petroleum, which as we noted in today's EOD post, lost $45 billion in market cap in 45 milliseconds (a collapse rate of $1 billion per millisecond), flash crashing from $90 all the way to an (allegedly illegal) stub quote of $0.01. http://www.zerohedge.com/news/2013-05-17/how-last-second-flash-crash-pushed-sp-500-1667-1666 How 10,000 Contracts Crashed The Market: A Visual Deconstruction Of Last Night's E-Mini Flash Crash http://www.zerohedge.com/news/2012-12-21/how-10000-contracts-crashed-market-visual-deconstruction-last-nights-e-mini-flash-cr Symantec Flash-Crash Destroys Over $1.5 Billion In Less Than A Second http://www.zerohedge.com/news/2013-04-30/symantec-flash-crash-destroys-over-15-billion-less-second This sort of thing happens so often, I don't pay much attention anymore." Is the stock's price at any given moment the price at which all shares could be sold to new investors? No.  For the simple fact that the current bid/offer always have sizes associated. What you should be looking at is the consolidated price to buy/sell X shares (10bn doesn't really work as not everyone is willing to sell/buy). If you look at the spread of the consolidated price at your quantity level, you'd notice it would be in stark contrast to the spread of the best bid/offer but (by definition) that would be the price to buy or sell X shares to new investors. Edit Calculation of the consolidated price of X shares: You go through the order book and calculate the size-weighted average price until you covered X. Example: So the consolidated price for 3000 shares would be $39.80, the consolidated price for 2000 shares would be $39.90.
I stock is only worth what someone will pay for it.  If you want to sell it you will get market price which is the bid. It depends completely on the current order book for that security.  There is literally no telling how that buy order would move the price of a stock in general. In order to see whether you can buy or sell some given quantity of a stock at the current bid price, you need a counterparty (a buyer) who is willing to buy the number of stocks you are wishing to offload. To see whether such a counterparty exists, you can look at the stock's order book, or level two feed. The order book shows all the people who have placed buy or sell orders, the price they are willing to pay, and the quantity they demand at that price. Here is the order book from earlier this morning for the British pharmaceutical company, GlaxoSmithKline PLC.  Let's start by looking at the left-hand blue part of the book, beneath the yellow strip. This is called the Buy side. The book is sorted with the highest price at the top, because this is the best price that a seller can presently obtain. If several buyers bid at the same price, then the oldest entry on the book takes precedence. You can see we have five buyers each willing to pay 1543.0 p (that's 1543 British pence, or £15.43) per share. Therefore the current bid price for this instrument is 1543.0. The first buyer wants 175 shares, the next, 300, and so on. The total volume that is demanded at 1543.0p is 2435 shares. This information is summarized on the yellow strip: 5 buyers, total volume of 2435, at 1543.0. These are all buyers who want to buy right now and the exchange will make the trade happen immediately if you put in a sell order for 1543.0 p or less. If you want to sell 2435 shares or fewer, you are good to go. The important thing to note is that once you sell these bidders a total of 2435 shares, then their orders are fulfilled and they will be removed from the order book. At this point, the next bidder is promoted up the book; but his price is 1542.5, 0.5 p lower than before. Absent any further changes to the order book, the bid price will decrease to 1542.5 p. This makes sense because you are selling a lot of shares so you'd expect the market price to be depressed. This information will be disseminated to the level one feed and the level one graph of the stock price will be updated. Thus if you have more than 2435 shares to sell, you cannot expect to execute your order at the bid price in one go. Of course, the more shares you are trying to get rid of, the further down the buy side you will have to go. In reality for a highly liquid stock as this, the order book receives many amendments per second and it is unlikely that your trade would make much difference. On the right hand side of the display you can see the recent trades: these are the times the trades were done (or notified to the exchange), the price of the trade, the volume and the trade type (AT means automatic trade).  GlaxoSmithKline is a highly liquid stock with many willing buyers and sellers. But some stocks are less liquid. In order to enable traders to find a counterparty at short notice, exchanges often require less liquid stocks to have market makers. A market maker places buy and sell orders simultaneously, with a spread between the two prices so that they can profit from each transaction. For instance Diurnal Group PLC has had no trades today and no quotes. It has a more complicated order book, enabling both ordinary buyers and sellers to list if they wish, but market makers are separated out at the top. Here you can see that three market makers are providing liquidity on this stock, Peel Hunt (PEEL), Numis (NUMS) and Winterflood (WINS). They have a very unpalatable spread of over 5% between their bid and offer prices. Further in each case the sum total that they are willing to trade is 3000 shares. If you have more than three thousand Dirunal Group shares to sell, you would have to wait for the market makers to come back with a new quote after you'd sold the first 3000. It depends to some extent on how you interpret the situation, so I think this is the general idea. Say you purchase one share at $50, and soon after, the price moves up, say, to $55. You now have an unrealized profit of $5. Now, you can either sell and realize that profit, or hold on to the position, expecting a further price appreciation. In either case, you will consider the price change from this traded price, which is $55, and not the price you actually bought at. Hence, if the price fell to $52 in the next trade, you have a loss of $3 on your previous profit of $5. This (even though your net P&L is calculated from the initial purchase price of $50), allows you to think in terms of your positions at the latest known prices. This is similar to a Markov process, in the sense that it doesn't matter which route the stock price (and your position's P&L) took to get to the current point; your decision should be based on the current/latest price level. I'd add, this is actually the way any stock opens every day, i.e. the closing price of the prior day is what it is, but the opening price will reflect whatever news there was prior to the day's open. If you watch the business news, you'll often see that some stock has an order imbalance and has not opened yet, at the normal time. So, as Geo stated, those who were sold shares at the IPO price paid $38, but then the stock could open at whatever price was the point where bid and ask balanced.   I snapped a screen capture of this chart on the first day of trading, the daily charts aren't archived where I can find them. This is from Yahoo Finance. You can see the $42 open from those who simply wanted in but couldn't wait, the willingness of sellers to grab their profit right back to what they paid, and then another wave of buying, but then a sell-off. It closed virtually unchanged from the IPO price. It seems like you want to compare the company's values not necessarily the stock price.  Why not get the total outstanding shares and the stock price, generate the market cap.  Then you could compare changes to market cap rather than just share price. I think he means that if he liquidated his shares of Amazon, the stock would fall. Depending on how much he actually owns, which I have no idea, it could cause the stock price to plummet.  In a more extreme scenario, a person that owns 40% of a company cannot liquidate their shares without the stock falling to ridiculously low levels. "Yes and no.  There are different classes of shares - Some have voting rights, some *don't*.  Some take precedence over others in a bankruptcy.  Some get larger dividends.  ""Common"" isn't really a useful description of your stake in the company.  You *do* have a ""stake"" in the company, but not all shares are equal." "To add to @keshlam's answer slightly a stock's price is made up of several components: the only one of these that is known even remotely accurately at any time is the book value on the day that the accounts are prepared. Even  completed cashflows after the books have been prepared contain some slight unknowns as they may be reversed if stock is returned, for example, or reduced by unforeseen costs.  Future cashflows are based on (amongst other things) how many sales you expect to make in the future for all time. Exercise for the reader: how many iPhone 22s will apple sell in 2029? Even known future cashflows have some risk attached to them; customers may not pay for goods, a supplier may go into liquidation and so need to change its invoicing strategy etc.. Estimating the risk on future cashflows is highly subjective and depends greatly on what the analyst expects the exact economic state of the world will be in the future. Investors have the choice of investing in a risk free instrument (this is usually taken as being modelled by the 10 year US treasury bond) that is guaranteed to give them a return. To invest in anything riskier than the risk free instrument they must be paid a premium over the risk free return that they would get from that. The risk premium is related to how likely they think it is that they will not receive a return higher than that rate. Calculation of that premium is highly subjective; if I know the management of the company well I will be inclined to think that the investment is far less risky (or perhaps riskier...) than someone who does not, for example. Since none of the factors that go into a share price are accurately measurable and many are subjective there is no ""right"" share price at any time, let alone at time of IPO. Each investor will estimate these values differently and so value the shares differently and their trading, based on their ever changing estimates, will move the share price to an indeterminable level. In comments to @keshlam's answer you ask if there is enough information to work out the share price if a company buys out the company before IPO. Dividing the price that this other company paid by the relative ownership structure of the firm would give you an idea of what that company thought that the company was worth at that moment in time and can be used as a surrogate for market price but it will not and cannot accurately represent the market price as other investors will value the firm differently by estimating the criteria above differently and so will move the share price based on their valuation." "It reminds me of the Efficient Market Hypothesis, except that just states in its weakest form that the current market price accounts for all information embedded in previous market prices. In other words, people buying today at 42 know it was selling for 40 yesterday, and the patterns and such. To say that stock is memoryless strikes me as not quite right -- to the extent that stocks are valued based on earnings, much of what we infer about future earnings relies on past and present earnings. One obvious counterexample to this ""memoryless"" claim is bankruptcy. If a stock files bankruptcy, and there isn't enough money to pay senior debt, your shares are worth 0 in perpetuity." Ask yourself a better question: Under my current investment criteria would I buy the stock at this price? If the answer to that question is yes you need to work out at what price you would now sell out of the position. Think of these as totally separate decisions from your original decisions to buy and at what price to sell. If you would buy the stock now if you didn't already hold a position then you should keep that position as if you had sold out at the price that you had originally seen as your take profit level and bought a new position at the current price without incurring the costs. If you would not buy now by those criteria then you should sell out as planned. This is essentially netting off two investing decisions. Something to think about is that the world has changed and if you knew what you know now then you would probably have set your price limit higher. To be disciplined as an investor also means reviewing current positions frequently and without any sympathy for past decisions. You would think that share prices is just a reflection of how well the company is doing but that is not always the case. Sometimes it reflects the investor confidence in the company more than the mere performance. So for instance if some oil company causes some natural disaster by letting one of there oil tankers crash into a coral reef then investor confidence my take a big hit and share prices my fall even if the bottom line of the company was not all that effected. P/E is the number of years it would take for the company to earn its share price.  You take share price divided by annual earnings per share.  You can take the current reported quarterly earnings per share times 4, you can take the sum of the past four actual quarters earnings per share or you can take some projected earnings per share. It has little to do with a company's actual finances apart from the earnings per share.  It doesn't say much about the health of a company's balance sheet, and is definitely not an indicator for bankruptcy.  It's mostly a measure of the market's assumptions of the company's ability to grow earnings or maintain it's current earnings growth.   A share price of $40 trading for a P/E ratio of 10 means it will take the company 10 years to earn $40 per share, it means there's current annual earnings per share of $4.  A different company may also be earning $4 per share but trade at 100 times earnings for a share price of $400.  By this measure alone neither company is more or less healthy than the other.  One just commands more faith in the future growth from the market. To circle back to your question regarding a negative P/E, a negative P/E ratio means the company is reporting negative earnings (running at a loss).  Again, this may or may not indicate an imminent bankruptcy.  Increasing balance sheet debt with decreasing revenue and or earnings and or balance sheet assets will be a better way to assess bankruptcy risk. "Someone who buys a stock is fundamentally buying a share of all future dividends, plus the future liquidation value of the company in the event that it is liquidated.  While some investors may buy stocks in the hope that they will be able to find other people willing to pay more for the stock than they did, that's a zero sum game.  The only way investors can make money in the aggregate is if either stocks pay dividends or if the money paid for company assets at liquidation exceeds total net price for which the company sold shares. One advantage of dividends from a market-rationality perspective is that dividend payments are easy to evaluate than company value.  Ideally, the share price of a company should match the present per-share cash value of all future dividends and liquidation, but it's generally impossible to know in advance what that value will be.  Stock prices may sometimes rise because of factors which increase the expected per-share cash value of future dividends and liquidations. In a sane market, rising prices on an item will reduce people's eagerness to buy and increase people's eagerness to sell.  Unfortunately, in a marketplace where steady price appreciation is expected the feedback mechanisms responsible for stability get reversed.  Rapidly rising prices act as a red flag to buyers--unfortunately, bulls don't see red flags as signal to stop, but rather as a signal to charge ahead. For a variety of reasons including the disparate treatment of dividends and capital gains, it's often not practical for a company to try to stabilize stock prices through dividends and stock sales.  Nonetheless, dividends are in a sense far more ""real"" than stock price appreciation, since paying dividends generally requires that companies actually have sources of revenues and profits.  By contrast, it's possible for stock prices to go through the roof for companies which have relatively few assets of value and no real expectation of becoming profitable businesses, simply because investors see rising stock prices as a ""buy"" signal independent of any real worth." "The only thing that makes a stock worthless is when the company goes out of business. Note that bankruptcy, by itself, does not mean the company is closing. It could successfully restructure its affairs and come out of bankruptcy with a better outlook. Being a small or unprofitable business may cause a company's to trade in the ""penny stock"" range, but there is still some value there. Since most dying companies will pass through the penny stock phase, you may be able to track down what you're looking for by finding companies who have been (or are about to be) delisted. Delisting is not death, it's just the point at which the company's shares no longer meet the qualifications to be traded on a particular exchange. If you find old stock certificates in your grandmother's sock drawer, they may be a treasure, or they may be worthless pieces of paper if the company changed its ownership and Grandma didn't know about it."