What could be the cause of a extreme high/low price in after hours market?
"Often these types of trades fall into two different categories.   An error by broker or exchange.  Exchange clearing out part of their books incorrectly is an example.  Most exchanges make firms reopen their positions for after market hours.  There may have been an issue doing so or exchange could incorrectly cancel positions.  I was in the direct feed industry for years and this was a big issue.  At the same time the broker can issue a no limit buy on accident (or has software that is prospecting and said software has a bug or written poorly).   unscrupulous parties looking to feign an upswing or downswing in market.  Let's say you hold 500k shares in a stock that sells for $11.  You could possibly buy 100 shares for $13.  Trust me you will find a seller.  Then you are hoping that people see that trade as a ""norm"" and trade from there, allowing you to rake in $1M for spending an extra $200 - NOTE this is not normal and an extreme example.  This was so common in the early days of NASDAQ after hours that they discontinued using the after hours trades as part of historical information that they keep like daily/yearly high or closing price.  The liquidity allows for manipulation.  It isn't seen as much now since this has been done a million times but it does still happen." Many of the above comments are correct about illiquidity.  If someone needs to trade at a time of low liquidity, for instance when the markets are closed, the bid/ask spread can often be large to induce someone to trade at odd times.  Especially as the broker/bank on the other side of the trade can't immediately go to the market to close out the risk as they often prefer to do. In this case the jump is actually is large but not that large (~4%).  Note this trade price is near the close price on the day before. The system I use shows a trade that evening for 5 shares near the price on the graph.  If you called me after I was done with work and tried to buy 5 shares I'd quote you a bad price too.
The last column in the source data is volume (the number of stocks that was exchanged during the day), and it also has a value of zero for that day, meaning that nobody bought or sold the stocks on that day. And since the prices are prices of transactions (the first and the last one on a particular day, and the ones with the highest/lowest price), the prices cannot be established, and are irrelevant as there was not a single transaction on that day. Only the close price is assumed equal to its previous day counterpart because this is the most important value serving as a basis to determine the daily price change (and we assume no change in this case). Continuous-line charts also use this single value. Bar and candle charts usually display a blank space for a day where no trade occurred. Apparent data-feed issues coming out of NASDAQ in the after hours market. Look at MSFT, AMZN, AAPL, heck even Sears.      Funny thing though, is that you see traces of irregular prices during the active session around 10:20am on stocks like GOOG. Depends on when you are seeing these bids & asks-- off hours, many market makers pull their bid & ask prices entirely.  In a lightly traded stock there may just be no market except during the regular trading day. "Investopedia's explanation of overbought: An asset that has experienced sharp upward movements over a very short period of time is often deemed to be overbought. Determining the   degree in which an asset is overbought is very subjective and can   differ between investors. Technicians use indicators such as the relative strength index, the stochastic oscillator or the money flow index to identify securities   that are becoming overbought. An overbought security is the opposite of one that is oversold. Something to consider is the ""potential buyers"" and ""potential sellers"" of a stock. In the case of overbought, there are many more buyers that have appeared and driven the price to a point that may be seen as ""unsustainably high"" and thus may well come down soon if one looks at the first explanation. For oversold, consider the flip side of this. A real life scenario here would be to consider airline tickets where a flight may be ""overbooked"" that could also be seen as ""oversold"" in that more tickets were sold than seats that are available and thus people will be bumped as not all tickets can be honored in this case. For a stock scenario of ""oversold"" consider how IPOs work where several buyers have to exist to buy the shares so the investment bank isn't stuck holding them which sends up the price since the amount wanted by the buyers may be more than what can be sold. The price shifts in bringing out more of one side than the other is the point you are missing. In shifting the price up, this attracts more sellers to satisfy the buyers. However, if there is a surge of buyers that flood the market, then there could be a perception that the security is overbought in the sense that there may be few buyers left for the security and thus the price may fall in the near term. If the price is coming down, this attracts more buyers to achieve the other side. The potential part is what you don't see and I wonder if you can imagine this part of the market. The airline example I give as an example as you don't seem to think either side of buying or selling can be overloaded. In the case of an oversold flight, there were more seats sold than available so yes it is possible. Stocks exist in finite quantities as there are only X shares of a company trading at any one time if you look into the concept of a float." "I've alway thought that it was strange, but the ""price"" that gets quoted on a stock exchange is just the price of the last transaction. The irony of this definition of price is that there may not actually be any more shares available on the market at that price. It's also strange to me that the price isn't adjusted at all for the size of the transaction. A transaction of just 1 share will post a new price even if just seconds earlier 100,000 shares traded for a different price. (Ok, unrealistic example, but you get my point.) I've always believed this is an odd way to describe the price. Anyway, my diatribe here is supposed to illustrate the point that the fluctuations you see in price don't really reflect changing valuations by the stock-owning public. Each post in the exchange maintains a book of orders, with unmatched buy orders on one side and unmatched sell orders on the other side. If you go to your broker and tell him, ""fill my order for 50,000 shares at market price"", then the broker won't fill you 50,000 shares at .20. Instead, he'll buy the 50 @ .22, then 80 @ .23, then 100 @ .30, etc. Because your order is so large compared to the unmatched orders, your market order will get matched a bunch of the unmatched orders on the sell side, and each match will notch the posted price up a bit. If instead you asked the broker, ""open a limit order to buy 50000 shares at .20"", then the exchange will add your order to the book: In this case, your order likely won't get filled at all, since nobody at the moment wants to sell at .20 and historically speaking it's unlikely that such a seller will suddenly appear. Filling large orders is actually a common problem for institutional investors: http://www.businessweek.com/magazine/content/05_16/b3929113_mz020.htm http://www.cis.upenn.edu/~mkearns/papers/vwap.pdf (Written by a professor I had in school!)" It does sometimes open one day the same as it closed the previous day.  Take a look at ESCA, it closed October 29th at 4.50, at opened November 1st at 4.50.  It's more likely to change prices overnight than it is between two successive ticks during the day, because a lot more time passes, in which news can come out, and in which people can reevaluate the stock. First - Google's snapshot -  Then - Yahoo -  I took these snapshots because they will not exist on line after the market opens, and without this context, your question won't make sense. With the two snapshots you can see, Yahoo shows the after hours trades and not just the official market close for the day. The amount it's down is exactly tracked from the close shown on Google. Now you know. You are correct, a possible Dead Cat Bounce is forming on the stock markets. If it does form it will mean that prices have not reached their bottom, as this pattern is a bearish continuation pattern. For a Dead Cat Bounce to form prices will need to break through support formed by the lows last week. If prices bounce off the support and go back up it could become a double bottom pattern, which is a reversal pattern. The double bottom would be confirmed if prices break above the recent high a couple of days ago. Regarding the psychology of the dead cat bounce pattern, is that after a distinct and quick reversal of prices from recent highs you have 2 groups of market participants who create demand in the market. Firstly you have those who were short covering their short positions to take profits, and secondly you have those who are looking for a bargain buying at what they think is the low. So for a few days you have the bulls taking over the bears.  Then as more less positive news comes in, the bears hit the market again. These are more participants opening short positions, but more so those who missed out in selling previously because prices fell too quickly, seeing another opportunity to sell at a better price. So the bears take over again.  Unless there is very good news around the corner it is likely that the bears will stay in control and prices will fall further. How to trade a dead cat bounce (assuming you have been stopped out of your long possistions already)? If you are aggressive you can go short as prices start reversing from the top of the bounce (with your stop loss just above the top of the bounce). If you are more conservative you would place your entry for a short position just below the support at the start of the bounce (with your stop above the top of the bounce). You could also place an order for a long position above the top of the bounce if a double bottom eventuated. A One Cancels the Other (OCO) would be an appropriate order for such a situation. It is called the Monday Effect or the Weekend Effect. There are a number of similar theories including the October Effect and January Effect. It's all pretty much bunk. If there were any truth to traders would be all over it and the resulting market forces would wipe it out. Personally, I think all technical analysis has very little value other than to fuel conversations at dinner parties about investments. You might also consider reading about Market efficiency to see further discussion about why technical approaches like this might, but probably don't work. "people are willing to pay higher premiums for options when stocks go down. Obviously the time value and intrinsic value and interests rates of the option doesn't change because of this so the miscalculation remainder is priced into the implied volatility part of the formula.  Basically, anything that suggests the stock price will get volatile (sharp moves in either direction) will increase the implied volatility of the option. For instance, around earnings reports, the IV in both calls and puts in the nearest expiration dates are very high. When stocks go down sharply, the volatility is high because some people are buying puts for protection and others are buying calls because they think there will be a rebound move in the other direction. People (the ""sleep-at-night"" investors, not the derivatives traders ;) )  tend to be calm when stocks are going up, and fearful when they are going down. The psychology is important to understand and observe and profit from, not to quantitatively prove. The first paragraph should be your qualitative answer" It looks more like someone is trying to pocket the spread.  The trades are going off at the bid then the ask (from what I can tell without any L1 and L2 data, but the spread could be bigger than what the prices show, since the stock looks pretty volatile given the difference between current price and VWAP...).  Looking through the JSE rule books I didn't find any special provisions on how they handle odd lots in their Central Order Book, but the usual practice in other markets is to display only round lot orders. So these 4 share orders would remain hidden from book participants and could be set there to trigger executions from those who are probing for limit orders. Or to make a market with very limited risk. 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. I hate attributing an event like this to a single cause.  That implies that the market is an orderly system where everything operates smoothly.  I prefer to see it as much chaotic. When I see a drop like that happen, I'd say that there were a lot of sellers of stocks and all the buyers were bidding less and less for those few minutes.  Perhaps the catalyst for that was a typo or a strange order.  But in the end all the participants in the market responded by bidding down stocks, not just one person.  It takes sides to complete a trade. I know my model is a bit simplistic...  I'd be happy if someone corrected me :-) Ultimately no one really knows what causes the markets to rise and fall beyond supply and demand. If more people want to buy then sell, prices go up. And if more people want to sell, prices go down. The news channels will often try to attribute a specific reason to the price move, but that is largely just guess work to fill up the news pages so people have something to read. You may find it interesting to read up on the Elliot wave principle. The crash of 2008 was a perfect Elliot Wave fit. Elliot Wave theory states that social moods (which ultimately drive the stock market) generally occur in a relatively predictable pattern. The crash in September was a Wave 3 down. This is where the majority of people give up hope. However there are still a few people who are still holding on. The markets tend to meander about during wave 4. Finally the last few people give up hope and sell out. This causes the final crash of wave 5. Only when the last person has given up hope can the markets start to go up again.. The two answers so far are right, but there's a third factor - for many stocks, there's after hours trading. So the official 4PM close is not what the stock's last trade was when they open again. Regardless, even that after hour price is not the starting point as Muro points out.