Large orders and market manipulation
"If you own a stake large enough to do that, you became regulated - under Section 13(d) of the 1934 Act and Regulation (in case of US stock) and you became regulated. Restricting you from ""shocking"" market. Another thing is that your broker will probably not allow you to execute order like that - directed MKT order for such volume. And market is deeper than anyone could measure - darkpools and HFTs passively waiting for opportunities like that."
More shares mean less volatility because it takes a larger number of trades, a larger number of shares per trade, or a combination of both to raise or lower the stock price. Institutional investors (mutual funds, pensions, hedge funds, other investment firms, etc) are the sorts of organizations with the large amounts of money needed to move a stock price one way or the other.  But the more floating shares there are in a company, the harder it is for one or two firms to move a stock price.  A company with fewer floating shares wouldn't require as many trades (or as many shares per trade) to see wider swings in price. When it comes to stock price, insider trading isn't the same as manipulation.  In the (surprisingly few) cases of insider trading that are prosecuted, it tends to be an individual (or small group) with early access to information that the broader market doesn't have being able to buy or sell ahead of the broader market.  Their individual sales are seldom if ever enough to noticeably move a stock price.  They're locking in profit or limiting a loss.  Manipulation might (but doesn't always) precede insider trading, if misinformation (or truth) is released for the purpose of creating a situation that can be profited from via a trade or trades. But what about the following scenario which is my paraphrasing of a Nanex article (I'm hoping you can help clarify this for me).  1. I observe a 1,000 lot @$10 advertised for Sell on a lit exchange.  2. I try to lift the 1,000 by placing a limit order @10.  3. My order goes through some kind of order routing process. First, 3 orders get executed on a dark pool. Let's say I got a 50 lot filled (so available offer reduces to 950).  4. My order hits a lit exchange. I get a partial fill for 100 (offer shrinks to 850); but the offered size shrinks instead to 500. Or 0.  5. Now, in order to execute my trade, I will have to take a higher price than the original advertised liquidity.  My question (maybe you can answer this) is why did my original order size of 1,000 appear in smaller blocks? Is this because the order routing algorithm breaks up the size?  Or is it that market makers only post offers in small block sizes (e.g. 100) So even if the order book looked like:  100 @ 10  100 @ 10  100 @ 10  100 @ 10  100 @ 10  100 @ 10  All the way to 1,000 total -- as soon as the first 100 shares were lifted, the MM can immediately cancel the remainder of the advertised liquidity -- in practical terms making it impossible to execute large orders at an advertised price. "That article, like almost any article written by a non-expert and quoting only ""research"" from lobbying groups, hugely misses the point. The vast majority of orders that end up being cancelled are cancelled as a standard part of exchanges' official market-maker programs. Each exchange wants you and me to know that it has liquidity -- that when we go to buy or sell some stock, there will be someone waiting on the other side of the trade.  So the exchange pays (via lowered fees or even rebates) hundreds of registered market makers to constantly have orders resting in each product's order book within a few ticks of the current NBBO or the last trade price.  That way, if everyone else should suddenly disappear from the market, you and I will still be able to trade our shares for a price somewhat close to the last trade price. But market makers who are simply acting in this ""backstop"" role don't actually want to have their orders filled, because those orders will almost always lose them money. So as prices rise and fall (as much as tens of times per second), the market makers need to cancel their resting orders (so they don't get filled) and add new ones at new prices (so they meet their obligations to the exchange).  And because the number of orders resting in any given product's order book is vastly larger than the number of actual trades that take place in any given time period, naturally the number of cancellations is also going to hugely outweigh the number of actual trades.  As much as 97% to 3% (or even more). But that's completely fine! You and I don't have to care about any of that.  We almost never need the market makers to be there to trade with us.  They're only there as a backstop.  There's almost always plenty of organic liquidity for us to trade against.  Only in the rare case where liquidity completely dries up do we really care that the registered market makers are there.  And in those cases (ideally) the market makers can't cancel their orders (depending on how well the exchange has set up its market maker program). So, to answer your question, the effect of standard order cancellation on a stock is essentially none.  If you were to visualize the resting orders in a product's book as prices moved up and down, you would essentially see a Gaussian distribution with mean at the last trade price, and it would move up and down with the price.  That ""movement"" is accomplished by cancellations followed by new orders. P.S. As always, keep in mind that your and my orders almost never actually make it to a real stock exchange anymore.  Nowadays they are almost always sent to brokers' and big banks' internal dark pools.  And in there you and I have no idea what shenanigans are going on.  As just one example, dark pools allow their operators and (for a fee) other institutional participants access to a feature called last look that allows them to cancel their resting order as late as after your order has been matched against it! :( Regarding the question in your comment ... If Alice is sending only bona fide orders (that is, only placing an order at time T if, given all the information she has at time T, she truly wants and intends for it to be filled) then her cancellation at a later time actually adds to the effectiveness of and public perception of the market as a tool for price discovery (which is its ultimate purpose). [In the following example imagine that there are no such things as trading fees or commissions or taxes.] Let's say Alice offers to buy AAPL at $99.99 when the rest of the market is trading it for $100.00.  By doing so she is casting her vote that the ""fair value"" of a share of AAPL is between $99.99 and $100.00. After all, if she thought the fair value of a share of AAPL was higher --  say, between $100.00 and $100.01 -- then she should be willing to pay $100.00 (because that's below fair value) and she should expect that other people in the market will not soon decide to sell to her at $99.99. If some time later Alice does decide that the fair value of AAPL is between $100.00 and $100.01 then she should definitely cancel her order at $99.99, for exactly the reason discussed above.  She probably won't get filled at $99.99, and by sitting there stubbornly she's missing out (potentially forever) on the possibility to make a profit. Through the simple act of cancelling her $99.99 order, Alice is once again casting a vote that she no longer thinks that's AAPL's fair value.  She is (very slightly) altering the collective opinion of the entire market as to what a share of AAPL is worth.  And if her cancellation then frees her up to place another order closer to her perceived fair value (say, at $100.00), then that's another vote for her honest optinion about AAPL's price. Since the whole goal of the market is to get a bunch of particpants to figure out the fair value of some financial instrument (or commodity, or smart phone, or advertising time, etc.), cancellations of honest votes from the past in order to replace them with new, better-informed honest votes in the present can only be a good thing for the market's effectiveness and perceived effectiveness. It's only when participants start sending non-honest votes (non bona fide orders) that things start to go off the rails.  That's what @DumbCoder was referring to in his comment on your original question." People are trying ideas like this, actually.  Though they generally aren't very public about it.  While keshlam ventures into hyperbole when mentioning Watson, he is certainly correct human language parsing is a extremely hard problem. While it is not always true that the big players will know before the news (sometimes that would qualify as insider trading).  The volume spike that you mention generally comes as the news arrives to the major (and minor) players.  So, if you have an algorithm run after the volume spike the price will likely have adjusted significantly already. You can try to avoid this by constantly scanning for news on a set of stocks however this becomes an even harder problem.  Or maybe by becoming more specific and parsing known important and specific news sources (farm report for instance) and trying to do so faster than anyone else.  These are some methods people use to not be too late. "You can interpret prices in any way you wish, but the commonly quoted ""price"" is the last price traded. If your broker routes those orders, unlikely because they will be considered ""unfair"" and will probably be busted by the exchange, the only way to drive the price to the heights & lows in your example is to have an overwhelming amount of quantity relative to the order book. Your orders will hit the opposing limit orders until your quantity is exhausted, starting from the best price to the worst price. This is the functional equivalent to a market order." Yes the stock market is 'rigged' to some extent but if you are good at game theory then you can predict the direction of bias and therefore take advantage of the 'rigged' nature of the market. Eventually enough people become aware of the bias and then the people who are manipulating the market have to change their strategy. This is just how the market works though its always worked this way it has just become more and more sophisticated.  look at it this way if you control billions of dollars in equities then you have to manipulate the market to give you a favorable price. If you dont manipulate then day traders and speculators will drive up the price of a security before you can even get your money in.  So the big players try to manipulate the market and the small fish try to predict the manipulation. Welcome to the jungle This depends on the stock exchange in question. Generally if you modify an existing order [including GTC], these are internally treated as Cancel/Replace Orders. Depending on the action, you may lose the time priority position and a new position would get assigned. More here. (f) Cancel/Replace Orders. Depending on how a quote or order is   modified, the quote or order may change priority position as follows: (1) If the price is changed, the changed side loses position and is   placed in a priority position behind all orders of the same type   (i.e., customer or non-customer) at the same price. (2) If one side's quantity is changed, the unchanged side retains its   priority position. (3) If the quantity of one side is decreased, that side retains its   priority position. (4) If the quantity of one side is increased, that side loses its   priority position and is placed behind all orders of the same type at   the same price. Ethereum trades are not subject to the same rules as securities are. Thats the primary flaw in your assessment. Yes, cryptocurrency is a free trading arena where you can actually take advantage of market inefficiencies yourself 24 hours a day, 7 days a week, at massive profits. The equity securities markets are not like that, and can't be used as a comparison. If you have a preference for flexibility, then it is already clear which markets work better for you. Market makers can make stub quotes, brokers can easily block their retail customers from doing it themselves. Even the dubious market manipulation excuse is reference to a sanction exclusive to the equity markets. The idea that it went through a week earlier probably triggered the compliance review. Yes, a broker can refuse to place your limit order. "The SEC reference document (PDF) explains order types in more detail. A fill-or-kill order is neither a market order nor a limit order; instead it's something in between. A market order asks to be filled at the best available price, whatever that price might be when the order gets to the exchange.  Additionally, if there are not enough counterparties to fill the order at the best available price, then part of the order may be filled at a worse price.  This all happens more or less immediately; there's no way to cancel it once it has been placed. A limit order asks to be filled at a particular price, and if no counterparties want to trade at that price right now, then the order will just sit around all day waiting for someone to agree on the price; it can be canceled at any time. A fill-or-kill order asks to be filled at a particular price (like a limit order), but if that price or a better one is not currently available then the order is immediately canceled.  It does not accept a worse price (the way a market order does), nor does it sit around waiting (the way a limit order does).  Since the exchange computes whether to ""fill"" or ""kill"" the order as soon as it is arrives, there's also no way to cancel it (like a market order)." Patrick Byrne (CEO of Overstock.com) ran a somewhat interesting website awhile back called 'Deep Capture' which focused heavily on naked short selling and bear raids. He was called all sorts of names and many 'serious' journalist types brushed his allegations off.   His basic argument was that a cabal of hedge funds would simultaneously naked short a specific equity and then a coordinated group of journalists and message board jockeys would disparage the company as loudly and publicly as possible, driving the price down. Naked shorting is supposed to be illegal since you can hold the types of positions like in the linked article about Citigroup where the number of shares sold short actually exceeds the number of shares in existence.  The group he named was essentially a who's who of hedge funds and fraudsters and included many names of prominent politically active 'reformed' criminals from the S&amp;L days on Wall St. I can't remember how the cards fell, but the scheme allegedly involved Michael Milliken, Sam Antar (from Crazy Eddie's Fraud), Gary Weiss, Jim Cramer, etc etc.   It was a fascinating story.   Byrne actually followed through with several lawsuits (one of which was settled after a Rocker Partners paid Byrne $5 million dollars to settle).   The 'Deep Capture' site is down, but I [found a decent article](http://www.theregister.co.uk/2008/10/01/wikipedia_and_naked_shorting/print.html) that sums up some of the shenanigans, including a journalist sock-puppeting to edit Wikipedia, repeatedly denying it, being IP-traced to inside the DTCC building (the Wall St. entity responsible for clearing trades, including naked shorts). It could be that the contracts were bought at cheaper prices such as $.01 earlier in the day. What you see there with the bid and ask is the CURRENT bid and CURRENT ask. The high ask price means there is no current liquidity, as someone is quoting a very high ask price just in case someone really wants to trade that price. But as you said, no one would buy this with a better price on a closer strike price. The volume likely occurred at a different price than listed on the current ask. "It's a form of market manipulation.   It makes it look like there is high trading volume, which gets attention from speculators and technical traders who see a ton of volume and think that there is some kind of news announcement or something. People start buying it so they don't miss out on whatever it is that ""everyone else"" is doing, and the price goes up." 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. In general, how does a large open market stock sale affect prices? A very general answer, all other things being equal, the price will move down. However there is nothing general. It depends on total number of shares in market and total turn over for that specific shares. The order book for the day etc. What is the maximum percentage of a company you could sell per day before the trading freezes, and what factors matter? Every stock exchange has rules that would determine when a particular stock would be suspended from trading, generally a 10-20% swing [either ways]. Generally highly liquid stock or stock during initial listing are exempt from such limits as they are left to arrive the market price ...  A large sell order may or may not swing the price for it to get suspended. At times even a small order may do ... again it is specific to a particular stock. While it is true that this formula may have historically outperformed the market you have to keep one important thing in mind: once the formula is out in the open, the market inefficiency will disappear. Here is what I mean. Historically there have always been various inefficiencies in the market structure. Some people were able to find these and make good money off them. Invariably these people tend to write books about how they did it. What happens next is that lots of people get in on the game and now you have lots of buyers going after positions that used to be under-priced, raising demand and thus prices for these positions. This is how inter-exchange arbitrage disappeared. Its how high frequency trading is running itself into the ground. If enough demand is generated for an inefficiency, the said inefficiency disappears or the gains get so small that you can only make money off it with large amounts of capital. Keep in mind, as Graham said, there is no silver bullet in the stock market since you do not hold any data that is unavailable to everyone else.