For what dates are the NYSE and U.S. stock exchanges typically closed?
The NYSE publishes a list of holidays at its website.  New link: https://www.nyse.com/markets/hours-calendars Old link in the original answer that doesn't work now: http://www.nyse.com/about/newsevents/1176373643795.html Hope that helps! Stumbled upon this question, I've found the updated dates for 2016 and 2017 in a more permanent location. https://www.nyse.com/markets/hours-calendars "All public US equity exchanges are closed on the 9 US trading holidays (see below) and open on all other days.  Exchanges also close early (13:00 ET) on the Friday after Thanksgiving and on the day before Independence Day if Independence Day is being observed on a Tuesday, Wednesday, Thursday, or Friday.  (Some venues have extended trading hours as a matter of course; for them an ""early close"" might be later than 13:00 ET.) To answer the second question, yes, if you know NASDAQ's or AMEX's holiday schedule, then you know NYSE's (modulo the timing of their early close).  I'm not sure about the options exchanges; they're not regulated the same way and are a good example of exchanges with extended trading hours in the first place. The US trading holidays are as follows.  Note that trading holidays are not the same as federal or bank holidays, which include Columbus Day and Veterans Day but do not include Good Friday."
If the share is listed on a stock exchange that creates liquidity and orderly sales with specialist market makers, such as the NYSE, there will always be a counterparty to trade with, though they will let the price rise or fall to meet other open interest.  On other exchanges, or in closely held or private equity scenarios, this is not necessarily the case (NASDAQ has market maker firms that maintain the bid-ask spread and can do the same thing with their own inventory as the specialists, but are not required to by the brokerage rules as the NYSE brokers are).  The NYSE has listing requirements of at least 1.1 million shares, so there will not be a case with only 100 shares on this exchange. "In the US, a private company with less than 500 owners can dictate who can or can't become a shareholder (this is true in general, but I'm sure there are loopholes).   Prior to Google's IPO I could not buy shares in Google at any price.   The reason Google was ""forced"" to go public is the 500 shareholder rule.   At a high level, with 500 shareholders the company is forced to do some extra financial accounting and they no longer can control who owns a share of the company, allowing me to purchase shares of google at that point.  At that point, it typically becomes in the companies best interest to go public. See this article about Google approaching the 500 shareholder limit in 2003. Further, Sorkin is not quite correct that ""securities laws mandate that the company go public"" if by ""go public"" we mean list on a stock exchange, available for general purchase.   Securities laws mandate what has to be reported in financial reporting and when you have to report it. Securities laws also can dictate restrictions on ownership of stock and if a company can impose their own restrictions. A group of investors cannot force a company onto a stock exchange.   If shares of Facebook are already for sale to anyone, then having >500 shareholders will force Facebook to file more paperwork with the SEC, it won't force Facebook onto the NYSE or NASDAQ.   When that point is reached, it may be in Facebook's best interest to have an IPO, but they will not be required by law to do so. Update:  CNN article discusses likely Facebook IPO in 2012. When companies have more than 500   shareholders, they're required to make   significant financial disclosures --   though they can choose to remain   private and keep their stock from   trading publicly. However, most   companies facing mandatory disclosures   opt to go public. The Securities and Exchange Commission   gives businesses lots of time to   prepare for that milestone. Companies   have until 120 days after the end of   the fiscal year in which they cross   the 500-shareholder line to begin   making their disclosures. If Facebook   tips the scale this year, that gives   it until April 2012 to start filing   financial reports." A reason not to split your stock is that the value of the company might fall back again, and if its stock price falls below $1 it will be delisted from the NYSE. So if the value of your company grows tenfold so the shares go from $5 to $50, you do a ten-for-one split, and then its value shrinks back to where it started, you're off the stock exchange. "I may be underestimating your knowledge of how exchanges work; if so, I apologize.  If not, then I believe the answer is relatively straightforward. Lets say price of a stock at time t1 is 15$ .  There are many types of price that an exchange reports to the public (as discussed below); let's say that you're referring to the most recent trade price.  That is, the last time a trade executed between a willing buyer and a willing seller was at $15.00. Lets say a significant buy order of 1M shares came in to the market. Here I believe might be a misunderstanding on your part.  I think you're assuming that the buy order must necessarily be requesting a price of $15.00 because that was the last published price at time t1.  In fact, orders can request any price they want.  It's totally okay for someone to request to buy at $10.00.  Presumably nobody will want to sell to him, but it's still a perfectly valid buy order. But let's continue under the assumptions that at t1: This makes the bid $14.99 and the ask $15.00.  (NYSE also publishes these prices.) There aren't enough people selling that stock. It's quite rare (in major US equities) for anyone to place a buy order that exceeds the total available shares listed for sale at all prices.  What I think you mean is that 1M is larger than the amount of currently-listed sell requests at the ask of $15.00. So say of the 1M only 100,000 had a matching sell order and others are waiting. So this means that there were exactly 100,000 shares waiting to be sold at the ask of $15.00, and that all other sellers currently in the market told NYSE they were only willing to sell for a price of $15.01 or higher.  If there had been more shares available at $15.00, then NYSE would have matched them. This would be a trigger to the automated system to start increasing the price. Here is another point of misunderstanding, I think.  NYSE's automated system does not invent a new, higher price to publish at this point.  Instead it simply reports the last trade price (still $15.00), and now that all of the willing sellers at $15.00 have been matched, NYSE also publishes the new ask price of $15.01.  It's not that NYSE has decided $15.01 is the new price for the stock; it's that $15.01 is now the lowest price at which anyone (known to NYSE) is willing to sell.  If nobody happened to be interested in selling at $15.01 at t1, but there were people interested in selling at $15.02, then the new published ask would be $15.02 instead of $15.01 -- not because NYSE decided it, but just because those happened to be the facts at the time. Similarly, the new bid is most likely now $15.00, assuming the person who placed the order for 1M shares did not cancel the remaining unmatched 900,000 shares of his/her order.  That is, $15.00 is now the highest price at which anyone (known to NYSE) is willing to buy. How much time does the automated system wait to increment the price, the frequency of the price change and by what percentage to increment etc. So I think the answer to all these questions is that the automated system does none of these things.  It merely publishes information about (a) the last trade price, (b) the price that is currently the lowest price at which anyone has expressed a willingness to sell, and (c) the price that is currently the highest price at which anyone has expressed a willingness to buy. ::edit:: Oh, I forgot to answer your primary question. Can we estimate the impact of a large buy order on the share price? Not only can we estimate the impact, but we can know it explicitly.  Because the exchange publishes information on all the orders it knows about, anyone tracking that information can deduce that (in this example) there were exactly 100,000 shares waiting to be purchased at $15.00.  So if a ""large buy order"" of 1M shares comes in at $15.00, then we know that all of the people waiting to sell at $15.00 will be matched, and the new lowest ask price will be $15.01 (or whatever was the next lowest sell price that the exchange had previously published)." My take on this is that this reduces your liquidity risk. Stocks, bonds and many other investment vehicles on secondary markets you may think of are highly liquid but they still require that markets are open and then an additional 3-5 business days to settle the transaction and for funds to make their way to your bank account.  If you require funds immediately because of an emergency, this 3-5 business days (which gets longer as week-ends and holidays are in the way) can cause a lot of discomfort which may be worth a small loss in potential ROI.  Think of your car breaking down or a water pipe exploding in your home and having to wait for the stock sale to process before you can make the payment. Admittedly, you have other options such as margin loans and credit cards that can help absorb the shock in such cases but they may not be sufficient or cause you to pay interest or fees if left unpaid. The CBOE site, as well as some other sites and trading platforms, will show the bid/ask and statistics for that option at each individual options exchange, in addition to statistics and the best bid/offer across all exchanges. cboe.com: Delayed Quote Help lists what the single-letter codes mean. A is for the AMEX options exchange, B is for BOX, X is for PHLX, etc. "In the US, stocks are listed on one exchange but can be traded on multiple venues.  You need to confirm exactly what your data is showing: a) trades on the primary-listed exchange; or b) trades made at any venue. Also, the trade condition codes are important.  Only certain trade condition codes contribute towards the day's open/high/low/close and some others only contribute towards the volume data.  The Consolidated Tape Association is very clear on which trades should contribute towards each value - but some vendors have their own interpretation (or just simply an erroneous interpretation of the specifications). It may surprise you to find that the majority of trading volume for many stocks is not on their primary-listed exchange.  For example, on 2 Mar 2015, NASDAQ:AAPL traded a total volume across all venues was 48096663 shares but trading on NASDAQ itself was 12050277 shares. Trades can be cancelled.  Some data vendors do not modify their data to reflect these busted trades.   Some data vendors also ""snapshot"" their feed at a particular point in time of the data.  Some exchanges can provide data (mainly corrections) 4-5 hours after the closing bell.  By snapshotting the data too early and throwing away any subsequent data is a typical cause of data discrepancies.   Some data vendors also round prices/volumes - but stocks don't just trade to two decimal places. So you may well be comparing two different sets of trades (with their own specific inclusion rules) against the same stock.  You need to confirm with your data sources exactly how they do things. Disclosure: Premium Data is an end-of-day daily data vendor." You seem to think that stock exchanges are much more than they actually are. But it's right there in the name: stock exchange. It's a place where people exchange (i.e. trade) stocks, no more and no less. All it does is enable the trading (and thereby price finding). Supposedly they went into mysterious bankruptcy then what will happen to the listed companies  Absolutely nothing. They may have to use a different exchange if they're planning an IPO or stock buyback, that's all. and to the shareholder's stock who invested in companies that were listed in these markets ?  Absolutley nothing. It still belongs to them. Trades that were in progress at the moment the exchange went down might be problematic, but usually the shutdown would happen in a manner that takes care of it, and ultimately the trade either went through or it didn't (and you still have the money). It might take some time to establish this. Let's suppose I am an investor and I bought stocks from a listed company in NYSE and NYSE went into bankruptcy, even though NYSE is a unique business, meaning it doesn't have to do anything with that firm which I invested in. How would I know the stock price of that firm  Look at a different stock exchange. There are dozens even within the USA, hundreds internationally. and will I lose my purchased stocks ?  Of course not, they will still be listed as yours at your broker. In general, what will happen after that ?  People will use different stock exchanges, and some of them migth get overloaded from the additional volume. Expect some inconveniences but no huge problems.