Bid price… sudden Drop
An option gives you the option rather than the obligation to buy (or sell) the underlying so you don't have to exercise you can just let the option expire (so long it doesn't have an automatic expiry). After expiration the option is worthless if it is out of the money but other than that has no hangover. Option prices normally drop as the time value of the option decays. An option has two values associated with it; time value and exercise value. Far out of the money (when the price of the underlying is far from the strike price on the losing side) options only have time value whereas deep in the money options (as yours seems to be) has some time value as well as the intrinsic value of the right to buy (sell) at a low (high) price and then sell (buy) the underlying.  The time value of the option comes from the possibility that the price of the underlying will move (further) in your favour and make you more money at expiry. As expiry closes it is less likely that there will be a favourable mood so this value declines which can cause prices to move sharply after a period of little to no revaluing. Up to now what I have said applies to both OTC and traded options but exchange traded options have another level of complexity in their trading; because there are fewer traders in the options market the size of trade at which you can move the market is much lower. On the equities markets you may need to trade millions of shares to have be substantial enough to significantly move a price, on the options markets it could be thousands or even hundreds. If these are European style options (which sounds likely) and a single trading entity was holding a large number of the exchange traded options and now thinks that the price will move significantly against them before expiry their sell trade will move the market lower in spite of the options being in the money. Their trade is based on their supposition that by the time they can exercise the option the price will be below the strike and they will lose money. They have cashed out at a price that suited them and limited what they will lose if they are right about the underlying. If I am not correct in my excise style assumption (European) I may need more details on the trade as it seems like you should just exercise now and take the profit if it is that far into the money.
When you place a bid between the bid/ask spread, that means you are raising the bid (or lowering the ask, if you are selling). The NBBO (national best bid and offer) is now changed because of your action, and yes, certain kinds of orders may be set to react to that (a higher bid or lower ask triggering them), also many algorithms (that haven't already queued an order simply waiting for a trigger, like in a stop limit) read the bid and ask and are programmed to then place an order at that point. "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." 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. A lower Price/Book Value means company is undervalued. It could also mean something horribly wrong. While it may look like a good deal, remember; The reality that the share price did not move shows that there is nothing nefarious going on.  It is most likely some mutual fund offloading their position to another fund.   You can commonly see the play out at market openings if you have access to level II data.  You will see a big block sitting on both sides of the same bid/ask.  If you put in a higher bid (or vice versa) the two positions will move to match yours.  And when the market opens their trade will be transacted BEFORE yours, even though you are thinking ... 'well I put in my bid first'.  Obviously they have agreed to swap and agreed to use whatever value the market decides. It doesn't sound fishy at all to me. Just seems like you may be dealing with a company that has relatively light trading volume to begin with, meaning that small trades could easily make the price drop 8% (which isn't much if you're talking about a stocks in the $5 or less range. If someone sells at the bid and the bid happens to be 8% lower than the current price, that bid is now the price, hence the drop. The bid moving up afterward, just means that someone is now willing to place a higher order than what the last trade was, to try to get in. All the time. For high volume stocks, it may be tough to see exactly what's going on, e.g. the bid/ask may be moving faster than your connection to the broker can show you.  What I've observed is with options. The volume on some options is measured in the 10's or 100's of contracts in a day. I'll see a case where it's $1.80/$2.00 bid/ask, and by offering $1.90 will often see a fill at that price. Since I may be the only trade on that option in the 15 minute period and note that the stock wasn't moving more than a penny during that time, I know that it was my order that managed to fill between the bid/ask. Everyone and their grandmother has been expecting QE to taper since May 2013. If the drop is caused by that, then it shouldn't be too serious.  Also, can people stop comparing stuff to 2009? 2009 was a unique once-in-a-lifetime circumstance, and not indicative of actual market values. I can't say I know everything about the underlying details, but from what I understand, your limit buy adds to the bid side of open orders, and one possibility is that someone placed a market order to sell when the bid price for the stock fell to $10 which was matched to your open limit order. So using your terminology, I would say the spot bid price is what fell to $10, even if for a brief moment. Whether or not it is possible for your order to be filled when the limit buy price is deeper than the current bid price is beyond me. It may have something to do with lot sizes. On 2012/05/18 at 15:34:00 UTC (11:34:00 EDT) FB was in chaos mode.  The most recent public US trade at that moment was at $40.94, but in the next one second (i.e. before the clock hit 15:34:01) there were several dozen trades as low as $40.76 and as high as $41.00. On 2012/05/30 at 17:21:00 UTC (13:21:00 EDT) the most recent public US trade for FB was at $28.28. It this a real situation or is it a made up example? Because for a stock that has a last traded priced of $5 or $6 and volume traded over $4M (i.e. it seems to be quite liquid), it is hardly likely that the difference from bid to ask would be as large as $1 (maybe for a stock that has volume of 4 to 5 thousand, but not for one having volume of 4 to 5 million). In regards to your question, if you were short selling the order would go in exactly the same as if you were selling a stock you owned. So your order would be on the ask side and would need to be matched up with a price on the bid side for there to be a trade. The best ask is the lowest ask, and the best bid is the highest bid.  If the ask was lower than the bid then they crossed, and that would be a crossed market and quickly resolved. So the bid will almost always be cheaper than the ask. A heuristic is that a bid is the revenue of the stock at any given time while the ask is the cost, so the market will only ever offer a profit to itself not to the liquidity seeker. If examining the book vertically, all orders are usually sorted descending. Since the best ask is the lowest ask, it is on the bottom of the asks, and vice versa for the best bid. The best bid & best ask will be those closest since that's the narrowest spread and price-time priority will promise that a bid that crosses the asks will hit the lowest ask, the best possible price for the bidder and vice versa for an ask that crosses the best bid. No, this is misbehavior of sales software that tries to automatically find the price point which maximizes profit. There have been much worse examples. Ignore it. The robot will eventually see that no sales occurred and try a more reasonable price. Yes, but it must be remembered that these conditions only last for instants, and that's why only HFTs can take advantage of this. During 2/28/14's selloff from the invasion of Ukraine, many times, there were moments where there was overwhelming liquidity on the bid relative to the ask, but the price continued to drop. "Re: A trader when buying needs to buy at the ask price and when selling needs to sell   at the bid price. So how can a trade happen 'in between' the bid and ask? Saying the trade can happen ""in between"" the bid & ask is simplistic.  There is a time dimension to the market.  It's more accurate to say that an order can be placed ""in between"" the current best bid & ask (observed at time T=0), thus establishing a new level for one or the other of those quoted prices (observed at time T>0). If you enter a market order to buy (or sell), then yes, you'll generally be accepting the current best ask (or best bid) with your order, because that's what a market order says to do: Accept the current best market price being offered for your kind of transaction.  Of course, prices may move much faster than your observation of the price and the time it takes to process your order – you're far from being the only participant. Market orders aside, you are free to name your own price above or below the current best bid & ask, respectively. ... then one could say that you are placing an order ""in between"" the bid and ask at the time your order is placed.  However – and this is key – you are also moving one or the other of those quoted prices in the process of placing your above-bid buy order or your below-ask sell order. Then, only if somebody else in the market chooses to accept your new ask (or bid) does your intended transaction take place. And that transaction takes place at the new ask (or bid) price, not the old one that was current when you entered your order. Read more about bid & ask prices at this other question: (p.s. FWIW, I don't necessarily agree with the assertion from the article you quoted, i.e.: ""By looking for trades that take place in between the bid and ask, you can tell when a strong trend is about to come to an end.""  I would say: Maybe, perhaps, but maybe not.)"