Why would a stock opening price differ from the offering price?
The offering price is the price at which that IPO is, well, offered. Think of it as a suggested retail price. The opening price is the actual price at which trading begins, on a particular day, for a stock. That price depends on demand/overnight-orders/what-have-you. Think of this as the actual price in the store. "The offering price is what the company will raise by selling the shares at that price.  However, this isn't usually what the general public sees as often there will be shows to drive up demand so that there will be buyers for the stock.  That demand is what you see on the first day when the general public can start buying the stock.  If one is an employee, relative or friend of someone that is offered, ""Friends and Family"" shares they may be able to buy at the offering price. Pricing of IPO from Wikipedia states around the idea of pricing: A company planning an IPO typically appoints a lead manager, known as   a bookrunner, to help it arrive at an appropriate price at which the   shares should be issued. There are two primary ways in which the price   of an IPO can be determined. Either the company, with the help of its   lead managers, fixes a price (""fixed price method""), or the price can   be determined through analysis of confidential investor demand data   compiled by the bookrunner (""book building""). Historically, some IPOs both globally and in the United States have   been underpriced. The effect of ""initial underpricing"" an IPO is to   generate additional interest in the stock when it first becomes   publicly traded. Flipping, or quickly selling shares for a profit, can   lead to significant gains for investors who have been allocated shares   of the IPO at the offering price. However, underpricing an IPO results   in lost potential capital for the issuer. One extreme example is   theglobe.com IPO which helped fuel the IPO ""mania"" of the late 90's   internet era. Underwritten by Bear Stearns on November 13, 1998, the   IPO was priced at $9 per share. The share price quickly increased   1000% after the opening of trading, to a high of $97. Selling pressure   from institutional flipping eventually drove the stock back down, and   it closed the day at $63. Although the company did raise about $30   million from the offering it is estimated that with the level of   demand for the offering and the volume of trading that took place the   company might have left upwards of $200 million on the table. The danger of overpricing is also an important consideration. If a   stock is offered to the public at a higher price than the market will   pay, the underwriters may have trouble meeting their commitments to   sell shares. Even if they sell all of the issued shares, the stock may   fall in value on the first day of trading. If so, the stock may lose   its marketability and hence even more of its value. This could result   in losses for investors, many of whom being the most favored clients   of the underwriters. Perhaps the best known example of this is the   Facebook IPO in 2012. Underwriters, therefore, take many factors into consideration when   pricing an IPO, and attempt to reach an offering price that is low   enough to stimulate interest in the stock, but high enough to raise an   adequate amount of capital for the company. The process of determining   an optimal price usually involves the underwriters (""syndicate"")   arranging share purchase commitments from leading institutional   investors. Some researchers (e.g. Geoffrey C., and C. Swift, 2009) believe that   the underpricing of IPOs is less a deliberate act on the part of   issuers and/or underwriters, than the result of an over-reaction on   the part of investors (Friesen & Swift, 2009). One potential method   for determining underpricing is through the use of IPO Underpricing   Algorithms. This may be useful for seeing the difference in that ""theglobe.com"" example where the offering price is $9/share yet the stock traded much higher than that initially." The opening price is derived from new information received. It reflects the current state of the market. Opening Price Deviation (from Investopedia): Investor expectation can be changed by corporate announcements or   other events that make the news. Corporations typically make   news-worthy announcements that may have an effect on the stock price   after the market closes. Large-scale natural disasters or man-made   disasters such as wars or terrorist attacks that take place in the   afterhours may have similar effects on stock prices. When this   happens, some investors may attempt to either buy or sell securities   during the afterhours. Not all orders are executed during after-hours trading. The lack of   liquidity and the resulting wide spreads make market orders   unattractive to traders in after-hours trading. This results in a   large amount of limit or stop orders being placed at a price that is   different from the prior day’s closing price. Consequently, when the   market opens the next day, a substantial disparity in supply and   demand causes the open to veer away from the prior day’s close in the   direction that corresponds to the effect of the announcement, news or   event.
The same applies if you were looking for a business to buy: would you pay more for a business that is doing well making increasing profits year after year, or for a business that is not doing so well and is losing money. A share in a company is basically a small part of a company which a shareholder can own. So would you rather own a part of a company that is increasing profits year after year or one that is continuously losing money? Someone would buy shares in a company in order to make a better return than they could make elsewhere. They can make a profit through two ways: first, a share of the company's profits through dividends, and second capital gains from the price of the shares going up. Why does the price of the shares go up over the long term when a company does well and increases profits? Because when a company increases profits they are making more and more money which increases the net worth of the company. More investors would prefer to buy shares in a company that makes increasing profits because this will increase the net worth of the company, and in turn will drive the share price higher over the long term. A company's increase in profits creates higher demand for the company's shares. Think about it, if interest rates are so low like they are now, where it is hard to get a return higher than inflation, why wouldn't investors then search for higher returns in good performing companies in the stock market? More investors' and traders' wanting some of the pie, creates higher demand for good performing stocks driving the share price higher. The demand for these companies is there primarily because the companies are increasing their profits and net worth, so over the long term the share price will increase in-line with the net worth. Over the short to medium term other factors can also affect the share price, sometime opposite to how the company is actually performing; however this is a whole different answer to a whole different question. "Market price is just the bid or offer price of the last sell or buy order in the market. The price that you actually receive or pay will be the price that the person buying the stock off you or selling it to you will accept. If there are no other participants in the market to make up the other side of your order (i.e. to buy off you if you are selling or to sell to you if you are buying) the exchange pays large banks to be ""market makers""; they fulfil your order using stocks that they don't want to either buy or sell just so that you get your order filled. When you place an order outside of market hours the order is kept on the broker's order books until the market reopens and then, at market opening time there is an opening ""auction"" at which orders are matched to opposing orders (i.e. each buy order will be matched with a sell) at a price determined by auction. You will not know what price the order was filled at until it has been filled. If you want to guarantee a price you can do so by placing a limit order that says not to pay more than a certain price for any unit of the stock." "Most of the time* you're selling to other investors, not back to the company. The stock market is a collection of bid (buy offers) and asks (sell offers). When you sell your stock as a retail investor at the ""market"" price you're essentially just meeting whatever standing bid offers are on the market.  For very liquid stocks (e.g. Apple), you can pretty much always get the displayed price because so many stocks are being traded. However during periods of very high volatility or for low-volume stocks, the quoted price may not be indicative of what you actually pay.  As an example, let's say you have 5 stocks you're trying to sell and the bid-side order book is 2 stocks for $105, 2 for $100, and 5 for $95. In this scenario the quoted price will be $105 (the best bid price), but if you accept market price you'll settle 2 for 105, 2 for 100, and 1 for 95. After your sell order goes through, the new quoted price will be $95. For high volume stocks, there will usually be so many orders near the midpoint price ($105, in this case) that you won't see any price slippage for small orders.  You can also post limit orders, which are essentially open orders waiting to be filled like in the above example. They ensure you get the price you want, but you have no way to guarantee they'll be filled or not.  Edit: as a cool example, check out the bitcoin GDAX on coinbase for a live example of what the order book looks like for stocks. You'll see that the price of bitcoin will drift towards whichever direction has the less dense order book (e.g. price drifts upwards when there are far more bids than asks.)" I think the simple answer to your question is: Yes, when you sell, that drives down the price. But it's not like you sell, and THEN the price goes down. The price goes down when you sell. You get the lower price.  Others have discussed the mechanics of this, but I think the relevant point for your question is that when you offer shares for sale, buyers now have more choices of where to buy from. If without you, there were 10 people willing to sell for $100 and 10 people willing to buy for $100, then there will be 10 sales at $100. But if you now offer to sell, there are 11 people selling for $100 and 10 people buying for $100. The buyers have a choice, and for a seller to get them to pick him, he has to drop his price a little. In real life, the market is stable when one of those sellers drops his price enough that an 11th buyer decides that he now wants to buy at the lower price, or until one of the other 10 buyers decides that the price has gone too low and he's no longer interested in selling. If the next day you bought the stock back, you are now returning the market to where it was before you sold. Assuming that everything else in the market was unchanged, you would have to pay the same price to buy the stock back that you got when you sold it. Your net profit would be zero. Actually you'd have a loss because you'd have to pay the broker's commission on both transactions. Of course in real life the chances that everything else in the market is unchanged are very small. So if you're a typical small-fry kind of person like me, someone who might be buying and selling a few hundred or a few thousand dollars worth of a company that is worth hundreds of millions, other factors in the market will totally swamp the effect of your little transaction. So when you went to buy back the next day, you might find that the price had gone down, you can buy your shares back for less than you sold them, and pocket the difference. Or the price might have gone up and you take a loss. 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. "After the initial public offering, the company can raise money by selling more stock (equity financing) or selling debt (e.g. borrowing money).  If a company's stock price is high, they can raise money with equity financing on more favorable terms.  When companies raise money with equity financing, they create new shares and dilute the existing shareholders, so the number of shares outstanding is not fixed. Companies can also return money to shareholders by buying their own equity, and this is called a share repurchase.  It's best for companies to repurchase their shared when their stock price is low, but ""American companies have a terrible track record of buying their own shares high and selling them low."" The management of a company typically likes a rising stock price, so their stock options are more valuable and they can justify bigger pay packages." "Your scenario depicts 2 ""in the money"" options, not ""at the money"". The former is when the share price is higher than the option strike, the second is when share price is right at strike. I agree this is a highly unlikely scenario, because everyone pricing options knows what everyone else in that stock is doing. Much about an option has everything to do with the remaining time to expiration. Depending on how much more the buyer believes the stock will go up before hitting the expiration date, that could make a big difference in which option they would buy. I agree with the others that if you're seeing this as ""real world"" then there must be something going on behind the scenes that someone else knows and you don't. I would tread with caution in such a situation and do my homework before making any move.   The other big factor that makes your question harder to answer more concisely is that you didn't tell us what the expiration dates on the options are. This makes a difference in how you evaluate them. We could probably be much more helpful to you if you could give us that information." The market is simply gapping at these times, some news may have come out that makes the market gap on the open from its previous close. Being FX, the market in one country might be trading and then at the start of the hour trading in a different country may commence, causing a small gap in price. Generally many things could cause the price to gap up or down, and these gaps sometime can occur at the start of a new hour or other timeframe you are using. They do tend to happen more often at the start of a new day's trading on a daily chart, especially with stocks.