What causes discontinuities with stock prices
During the 12 plus hours the market was closed news can change investors opinion of the stock. When the market reopens that first trade could be much different than the last trade the day before.
NO it was literally for one model while they needed a cheaper one before the model 3, this will never be part of their lineup again, and it was ONLY for a short period of time and ONLY on their cheapest car. Already discontinued, it's not what they do. "Not cumulative volatility. It's cumulative probability density. Time value isn't linear because PDFs (probability distribution function) aren't linear. It's a type of distribution e.g. ""bell-curves"") These distributions are based on empirical data i.e. what we observe. BSM i.e. Black-Scholes-Merton includes the factors that influence an option price and include a PDF to represent the uncertainty/probability. Time value is based on historical volatility in the underlying asset price, in this case equity(stock). At the beginning, time value is high since there's time until expiration and the stock is expected to move within a certain range based on historical performance. As it nears expiration, uncertainty over the final value diminishes. This causes probability for a certain price range to become more likely.  We can relate that to how people think, which affects the variation in the stock market price. Most people who are hoping for a value increase are optimistic about their chances of winning and will hold out towards the end. They see in the past d days, the stock has moved [-2%,+5%] so as a call buyer, they're looking for that upside. With little time remaining though, their hopes quickly drop to 0 for any significant changes beyond the market price. (Likewise, people keep playing the lottery up until a certain age when they're older and suddenly determine they're never going to win.)  We see that reflected in the PDF used to represent options price movements. Thus your time value which is a function of probability decreases in a non-linear fashion.  Option price = intrinsic value + time value At expiration, your option price = intrinsic value = stock price - strike price, St >= K, and 0 for St < K." "Feel free to educate man. Everything I can find says the same thing.  [Investopedia](http://www.investopedia.com/ask/answers/100314/what-are-key-factors-cause-market-go-and-down.asp)  &gt;If there are a greater number of buyers than sellers (more demand), the buyers bid up the prices of the stocks to entice sellers to get rid of them. Conversely, a larger number of sellers bids down the price of stocks hoping to entice buyers to purchase.  Yes, if a company is performing well, you might find that more people want to buy then sale.  That would cause it to go up.  But if no one wants to buy, it doesn't matter how well the company is doing.  I mean really, how would that work?  Someone in the company notices they had more sales today then yesterday, email someone on wallstreet and they just mouse wheel the stock price up to something higher?  Say the stock is $1.00 right now.  But the lowest buy order is $.90.  and the highest sale order is $1.10.  (I guess there is some math there making is $1.)  As soon as someone says, yeah.  I'll sale at 90 cents, it'll go down.  If someone says yeah, I'll buy at $1.10 it'll go up.    I'm sure there is more to it than that.  But everything I can find.  It 100% has to have people more people wanting to buy then sale for it to go up.  If more want to sale then buy, it'll go down.   But hey, if this is way off base.  Go ahead and fill me in.  I'm open to CMV.  This was all found after a short amount of time researching [""What makes stock prices go up?""](https://www.google.com/search?q=What+makes+stock+prices+go+up%3F&amp;oq=What+makes+stock+prices+go+up%3F&amp;gs_l=psy-ab.3..0i71k1l4.43421.43421.0.43882.0.0.0.0.0.0.0.0..0.0....0...1.1.64.psy-ab..0.0.0....0.6Crfejzb3XY)" "Part of it was an Oops, but not all of it. There were reports that the sudden   drop was caused by a trader who   mistyped an order to sell a large   block of stock. The drop in that   stock's price was enough to trigger   ""sell"" orders across the market. Source: http://www.msnbc.msn.com/id/36983596/ns/business-stocks_and_economy/" The satisfaction from gains packs less of an emotional impact than the fear of loss. It's very difficult for many people to overcome this fear, so when prices begin to fall, many investors sell to minimize their potential loss. This causes a further drop, which can lead to more selling as other investors reach their emotional threshold for loss. This emotion-based selling keeps the market inefficient in the short term. If there aren't enough value investors waiting to scoop up the stock at the new discount, it can stay undervalued for a long time. You should not look at volume in isolation but look at it together with other indicators and/or the release of news (good or bad). When there is lower than average volume this could be an indication that the stock is in a bit of a holding pattern, possibly waiting for some company or economic news to come out (especially when accompanied by small changes in price). It could also mean that trading in a certain direction is drying up and the trend is about to end (this could be accompanied with a large move in price). When there is higher than average volume (2 to 3 times more or higher), this could be due to the release of company results, company or economic news, or the start or end of a trend (especially if accompanied by a gap). A large increase in volume accompanied by a large fall in price (usually a gap down) may also be an indication the stock has gone ex-dividend. There could be a range of reasons for variations in volume to the average volume. That is why you need to look at other indicators, company reporting and news, and economic news in combination with the volume changes to get a grasp of what is really happening. Consider the price history to be the sum of short term movements and long term movements. If you hold a stock for a long time you will benefit (or lose) from its long term movement.  If a sufficiently large and very good short term trader existed he would tend to reduce short term volatility, eventually to nearly zero. At that point, the price would rise gently over the course of the day in line with the long term variation in price. Presumably robot traders will increase the time horizon of their trades when they have exhausted the gains they can make from short term trades. You say: Every time it seems the share price dips. Does it?  Have you collected the data?   It may just be that you are remembering the events that seem most painful at the time. To move the market with your trade you need to be dealing in a large amount of shares.    Unless the stock is illiquid (e.g most VCT in the UK), I don’t think you are dealing in that large a number; if you were then you would likely have access to a real time feed of the order book and could see what was going on.