What is the meaning of public stock price data from before the official first day of trading? [duplicate]
For the case of spinoffs it reflects the market as activities as the specific steps that have to be followed take place. For example the spinoff of Leidos from SAIC in 2013. (I picked this one becasue I knew some of the details) On September 9, 2013, the Board of Directors of SAIC, Inc.(Ticker   Symbol (NYSE):SAI) approved the following:  The separation of its technical, engineering and enterprise information technology services business through the distribution of   shares of SAIC  Gemini, Inc. to stockholders.  Each stockholder of   record of SAIC, Inc. as of  September 19, 2013 (Record Date) will   receive one (1) share of SAIC Gemini, Inc. common stock for every   seven (7) shares of SAIC, Inc. common stock  held by such stockholder   as of the Record Date.   This distribution will be effective after   market close on September 27, 2013 (Distribution Date).  After the   Distribution Date, SAIC Gemini, Inc. will be renamed Science   Applications International Corporation (New SAIC). A one (1) for four (4) reverse stock split of the SAIC, Inc. common stock effective as of Distribution Date. After the Distribution Date,   SAIC, Inc. will be renamed Leidos Holdings, Inc. (Leidos). Q 11: What are the different trading markets that may occur between   Record Date and Distribution Date? A: Beginning two days prior to the Record Date of September 19, 2013   through the Distribution Date on September 27, 2013, there may be   three different trading markets available with respect to SAIC, Inc.   and the separation. Stock Ticker – SAI (Regular Way Trading with Due Bills): Shares of SAI common stock that trade on the regular-way market will trade with   an entitlement to shares of the New SAIC common stock distributed on   the Distribution Date.  Purchasers in this market are purchasing both   the shares of Leidos and New SAIC common stock. Form of Stock Ticker –SAIC (When Issued Trading): Shares of New SAIC common stock may be traded on a “when-issued” basis.  These   transactions are made conditionally because the security has been   authorized, but not yet issued.  Purchasers in this market are only   purchasing the shares of  New SAIC common stock distributed on the   Distribution Date. Form of Stock Ticker – LDOS (Ex-Distribution Trading): Shares that trade on the ex-distribution market will trade without an entitlement   to shares of New SAIC common stock distributed on the Distribution   Date.  Purchasers in this market are only purchasing the shares of   Leidos common stock. So the stock price for New SAIC starts a few days before the record date of 19 September 2013, while LDOS (new name for the old SAIC) goes back much earlier. But the company didn't split until after the close of business on 27 September 2013. http://investors.saic.com/sites/saic.investorhq.businesswire.com/files/doc_library/file/GeneralStockholder-QuestionsandAnswers.pdf
Who's to say it wasn't priced into the markets, at least to some degree? Without any information on the behaviour of holders pre-expiry, no one can know if they've been shorting the stock in advance of selling on expiry day. And with the float being such a small proportion of the total issuance, there's always the risk of sudden fluctuations picking up big momentum - which could easily explain the 7% drop on expiry day. Add into all this uncertainty, the usual risks of shorting (e.g. limited upside, unlimited downside), and the observed phenomena aren't by any means killer blows of the Efficient Market Hypothesis. That's not to say that such evidence doesn't necessarily exist - just that this isn't it. Your order may or may not be executed.  The price of stock can open anywhere.  Often yesterday's close is a good indication of today's open, but with a big event overnight, the open may be somewhere quite different.  You'll have to wait and see like the rest of us.  Also, even if it doesn't execute at the open, the price could vary during the day and it might execute later. "I'm not sure the term actually has a clear meaning. We can think of ""what does this mean"" in two ways: its broad semantic/metaphorical meaning, and its mechanical ""what actual variables in the market represent this quantity"". Net buying/selling have a clear meaning in the former sense by analogy to the basic concept of supply and demand in equilibrium markets. It's not as clear what their meaning should be in the latter sense. Roughly, as the top comment notes, you could say that a price decrease is because of net selling at the previous price level, while a price rise is driven by net buying at the previous price level. But in terms of actual market mechanics, the only way prices move is by matching of a buyer and a seller, so every market transaction inherently represents an instantaneous balance across the bid/ask spread. So then we could think about the notion of orders. Actual transactions only occur in balance, but there is a whole book of standing orders at various prices. So maybe we could use some measure of the volume at various price levels in each of the bid/ask books to decide some notion of net buying/selling. But again, actual transactions occur only when matched across the spread. If a significant order volume is added on one side or the other, but at a price far away from the bid/offer - far enough that an actual trade at that price is unlikely to occur - should that be included in the notion of net buying/selling? Presumably there is some price distance from the bid/offer where the orders don't matter for net buying/selling. I'm sure you'd find a lot of buyers for BRK.A at $1, but that's completely irrelevant to the notion of net buying/selling in BRK.A. Maybe the closest thing I can think of in terms of actual market mechanics is the comparative total volumes during the period that would still have been executed if forced to execute at the end of period price. Assuming that traders' valuations are fixed through the period in question, and trading occurs on the basis of fundamentals (which I know isn't a good assumption in practice, but the impact of price history upon future price is too complex for this analysis), we have two cases. If price falls, we can assume all buyers who executed above the last price in the period would have happily bought at the last price (saving money), while all sellers who executed below the last price in the period would also be happy to sell for more. The former will be larger than the latter. If the price rises, the reverse is true." I found the answer. It was the Stock Ticker that I was looking for. So, if I understand correctly the price at certain moment is the price of the latest sale and can be used to get a global picture of what certain stock is worth at that certain instant. The Level 2 data is simply showing the depth of the market. If I am trading shares with my broker I have the option of viewing only the top 10 bid/ask prices in the depth or all of the data (which sometimes can be a very long list). With another broker I get the top ten bid and ask prices and how many orders are available for each price level, or I have the option of listing each order separately for each price level (in order of when the order was placed). I get the same kind of data if trading options. I do not know about futures because I don't trade them. Simply this data may be important to a trader because it may give an indication of whether there are more buyers or sellers in the market, which in turn may (but not always) give an indication of which way the market may be moving. As an example the price depth below shows WBC before market open with sellers outweighing the buyers in both numbers and volume.  This gives an indication that prices may drop when the market opens. Of course there could be some good news coming out prior to market open or just after, causing a flood of buyers into the market and sellers to cancel their orders. This would change everything around with more buyers than sellers and indicate that prices may now be going up. The market depth is an important aspect to look at before putting an order in, as it can give an indication of which way the market is moving, especially in a very liquid security or market. "A company whose stock is available for sale to the public is called a publicly-held or publicly-traded company.  A public company's stock is sold on a stock exchange, and anyone with money can buy shares through a stock broker. This contrasts with a privately-held company, in which the shares are not traded on a stock exchange. In order to invest in a private company, you would need to talk directly to the current owners of the company. Finding out if a company is public or private is fairly easy.  One way to check this is to look at the Wikipedia page for the company.  For example, if you take a look at the Apple page, on the right sidebar you'll see ""Type: Public"", followed by the stock exchange ticker symbol ""AAPL"".  Compare this to the page for Mars, Inc.; on that page, you'll see ""Type: Private"", and no stock ticker symbol listed. Another way to tell: If you can find a quote for a share price on a financial site (such as Google Finance or Yahoo Finance), you can buy the stock.  You won't find a stock price for Mars, Inc. anywhere, because the stock is not publicly traded." You need a source of delisted historical data.  Such data is typically only available from paid sources. According to my records 20 Feb 2006 was not a trading day - it was Preisdent's Day and the US exchanges were closed. The prior trading date to this was 17 Feb 2006 where the stock had the following data: Open: 14.40 High 14.46 Low 14.16 Close 14.32 Volume 1339800 (consolidated volume) Source: Symbol NVE-201312 within Premium Data US delisted stocks historical data set available from http://www.premiumdata.net/products/premiumdata/ushistorical.php Disclosure: I am a co-owner of Norgate / Premium Data. One of the fundamental of technical analysis suggests that holding a security overnight represents a huge commitment.  Therefore it would follow that traders would tend to close their positions prior to market close and open them when it opens. It is known as the range or the price spread of the stock. You can read more about it here http://www.investopedia.com/terms/r/range.asp The information on GOOG or other sites is the average price of the stock and is indicative of the price at with the stock would be available. The actual trades happen at different values throught the day ...  So the prices are good for most purposes and if you need the exact prices, you can thne decided to log into you trading terminal and get the actual quotes   This is similar to FX quotes or any other such quotes and give you a general sense There are several reasons why this may happen and I will update as I get more information from you. Volumes on that stock look low (supposing that they are either in a factor between 1s and 1000s) so it could well be that there was no volume on that day. If no trades occur then open, high and low are meaningless as they are statistics based on trades that occur that day and no trades occur. Remember that there has to be volume to get a price. The stock may have been frozen by either the exchange or the company for the day. This could be for various reasons including to prevent some illegal activity. In that case no trades were made because the market for that stock was closed. Another possibility is that all trades that day were cancelled by the exchange. The exchange may cancel all trades if there is unusual, potentially fraudulent or other illegal activity on the stock. In this case the last price for that day existed but was rolled back by the exchange and never occurred. This is a rare situation. Although I can't find any holidays on that date it is possible that this is how your data provider marks market holidays. It would be valid to ignore the data in that case as being from a non-market day. I cannot tell if this is possible without knowing exchange information. There is a possibility that some data providers don't receive data for a day or that it gets corrupted. It may be worth checking another source to ensure the integrity of the data that you are receiving. Whichever reason is true, the data provider has made the close equal to the previous day's close as no price movements occurred. Strictly the closing price is the price of the last trade made for that day and so should be null (and open, high and low should be null too and not 0 otherwise the price change on day is very large!). Therefore, to keep integrity, you have a few choices: "Company values (and thus stock prices) rely on a much larger time frame than ""a weekend"".  First, markets are not efficient enough to know what a companies sales were over the past 2-3 days (many companies do not even know that for several weeks).  They look at performance over quarters and years to determine the ""value"" of a company.  They also look forward, not backwards to determine value.  Prior performance only gives a hint of what future performance may be.  If a company shut its doors over a weekend and did no sales, it still would have value based on its future ability to earn profits." If I understand you correctly, you are noticing that a stock's price can change drastically when the time changes from pre-market trading hours to open market hours. This could occur because a much smaller pool of investors make trades during pre-market and after-market hours. When the regular market opens there is a large influx of trades, causing the prices to jump. When a stock is going to become public there's a level of analysis required to figure out the range of IPO price that makes sense. For a company that's somewhat mature, and has a sector to compare it to, you can come up with a range that would be pretty close. For the recent linkedin, it's tougher to price a somewhat unique company, running at a loss, in a market rich with cash looking for the next great deal. If one gives this any thought, an opening price that's so far above the IPO price represents a failure of the underwriters to price it correctly. It means the original owners just sold theirvshares for far less than the market thought they were worth on day one. The day of IPO the stock opens similar to how any stock would open at 9:30, there are bids and asks and a price at which supply (the ask) and demand (bid) balance. For this IPO, it would appear that there were enough buyers to push the price to twice the anticipated open and it's maintained that level since.  It's possible to have a different system in which a Dutch auction is used to make the shares public, in theory this can work, it's just not used commonly. That's the point.  They're crooks who only want to do an IPO at the moment they start filing publicly.  If you did an IPO after financials are already public, then you'd be forced to sell at a fair price.  Doing it before an actual earnings report (which is more accurate than an S-1) allows them to exploit speculation and get a better price.