How does an enlarged share base affect share price?
Most of the time when a stock splits to create more shares, it is done to bring the price per share down to a level that makes potential investors more comfortable. There are psychological reasons why some companies keep the price in the $30 to $60 range. Others like to have the price keep rising into the hundreds or thousands a share.  The split doesn't help current investors, with the possible exception that the news spurs interest in the stock which leads to a short term rise in prices; but it also doesn't hurt current investors. When a reverse stock split is done, the purpose is for one of several reasons:
"I may be underestimating your knowledge of how exchanges work; if so, I apologize.  If not, then I believe the answer is relatively straightforward. Lets say price of a stock at time t1 is 15$ .  There are many types of price that an exchange reports to the public (as discussed below); let's say that you're referring to the most recent trade price.  That is, the last time a trade executed between a willing buyer and a willing seller was at $15.00. Lets say a significant buy order of 1M shares came in to the market. Here I believe might be a misunderstanding on your part.  I think you're assuming that the buy order must necessarily be requesting a price of $15.00 because that was the last published price at time t1.  In fact, orders can request any price they want.  It's totally okay for someone to request to buy at $10.00.  Presumably nobody will want to sell to him, but it's still a perfectly valid buy order. But let's continue under the assumptions that at t1: This makes the bid $14.99 and the ask $15.00.  (NYSE also publishes these prices.) There aren't enough people selling that stock. It's quite rare (in major US equities) for anyone to place a buy order that exceeds the total available shares listed for sale at all prices.  What I think you mean is that 1M is larger than the amount of currently-listed sell requests at the ask of $15.00. So say of the 1M only 100,000 had a matching sell order and others are waiting. So this means that there were exactly 100,000 shares waiting to be sold at the ask of $15.00, and that all other sellers currently in the market told NYSE they were only willing to sell for a price of $15.01 or higher.  If there had been more shares available at $15.00, then NYSE would have matched them. This would be a trigger to the automated system to start increasing the price. Here is another point of misunderstanding, I think.  NYSE's automated system does not invent a new, higher price to publish at this point.  Instead it simply reports the last trade price (still $15.00), and now that all of the willing sellers at $15.00 have been matched, NYSE also publishes the new ask price of $15.01.  It's not that NYSE has decided $15.01 is the new price for the stock; it's that $15.01 is now the lowest price at which anyone (known to NYSE) is willing to sell.  If nobody happened to be interested in selling at $15.01 at t1, but there were people interested in selling at $15.02, then the new published ask would be $15.02 instead of $15.01 -- not because NYSE decided it, but just because those happened to be the facts at the time. Similarly, the new bid is most likely now $15.00, assuming the person who placed the order for 1M shares did not cancel the remaining unmatched 900,000 shares of his/her order.  That is, $15.00 is now the highest price at which anyone (known to NYSE) is willing to buy. How much time does the automated system wait to increment the price, the frequency of the price change and by what percentage to increment etc. So I think the answer to all these questions is that the automated system does none of these things.  It merely publishes information about (a) the last trade price, (b) the price that is currently the lowest price at which anyone has expressed a willingness to sell, and (c) the price that is currently the highest price at which anyone has expressed a willingness to buy. ::edit:: Oh, I forgot to answer your primary question. Can we estimate the impact of a large buy order on the share price? Not only can we estimate the impact, but we can know it explicitly.  Because the exchange publishes information on all the orders it knows about, anyone tracking that information can deduce that (in this example) there were exactly 100,000 shares waiting to be purchased at $15.00.  So if a ""large buy order"" of 1M shares comes in at $15.00, then we know that all of the people waiting to sell at $15.00 will be matched, and the new lowest ask price will be $15.01 (or whatever was the next lowest sell price that the exchange had previously published)." You have a lot of different questions in your post - I am only responding to the request for how to value the ESPP. When valuing an ESPP, don't think about what you might sell the shares for in the future, think about what the market would charge you for that option today. In general, an option is worth much less than the underlying share itself. For the simplest example, assume you work at a public company, and your exercise price for your options is $.30, and you can only exercise those options until the end of today, and the cost of the shares on the public stock exchange is also $.30. You have the same 'strike price' as everyone else in the market, making your option worth nothing. In truth, holding that right to a specific strike price into the future does give you value, because it means you can realize the upside in share price gains, without risking any money on share losses. So, how do you value the options? If it's a public company with an active options market, you can easily compare your $.30 strike price with the value of call options in the market that have a $.30 strike price. That becomes the value to you of the option (caveat: it is unlikely you can find an exact match for the terms of your vesting period, but you should be able to find a good starting point). If it's a public company without an active options market, you will have to do a bit of estimation. If a current share is worth $.25 (so, close to your strike price), then your option is worth a little bit, but not much. Compare other shares in your industry / company size to get examples of the relative value between an option and a share. If the current share price is worth $.35, then your option is worth about $.05 [the $.05 profit you could get by immediately exercising and selling, plus a bit more for an option on a share that you can't buy in the open market]. If it's a private company, then you need to be very clear on how shares are to be valued, and what methods you have available to sell back to the company / other individuals. You can then consider as per above, how to value the option for a share, vs the share itself. Without a clear way to sell your shares of a private company [ideally through a sale directly back to the company that you are able to force them to agree on; ie: the company will buyback shares at 5x Net income for the previous year, or something like that], then the value of a small number of shares is very nebulous. There is an extremely limited market for shares of private companies, if you don't own enough to exert control. In your case, because the valuation appears to be $2/share [be sure that these are the same share classes you have the option to buy], your option would be worth a little more than $1.70, if you didn't have to wait 4 years to exercise it. This would be total compensation of about $10k, if you were able to exercise today. Many people don't end up working for an early job in their career for 4 years, so you need to consider whether how much that will reduce the value of the ESPP for you personally. Compared with salary of 90k, 10k worth of stock in 4 years may not be a heavy motivating compensation consideration. Note also that because the company is not public, the valuation of $2/share should be taken with a grain of salt. During a stock split the only thing that changes is the number of shares outstanding.  Typically a stock splits to lower its price per share.  Sometimes if a company's value is falling it will do a reverse split where X shares will be exchanged for Y shares.  This is typically done to avoid being de-listed from an exchange if the price per share falls below a certain threshold, usually $1.  Again the only thing changing is the number of shares outstanding.  A 20 for 1 reverse split means for every 20 shares outstanding the shareholder will be granted one new share. Example X Co. has 1,000,000 shares outstanding for a price of $100 per share.  It does a 1 for 10 split.  Now there are 10,000,000 shares outstanding for a price of $10 per share. Example Y Co has 1,000,000 shares outstanding for a price of $1 per share.  It does a 10 for 1 reverse split.  Now there are 100,000 shares outstanding for a price of $10. Quickly looking at the news for ASTI it looks like it underwent a 20 for 1 reverse split.  You should probably look at your statements and ask your broker how the arithmetic worked in your case. Investopedia links for Reverse Stock Split and Stock Split "Market cap is the current value of a company's equity and is defined as the current share price multiplied by the number of shares. Please check also ""enterprise value"" for another definition of a company`s total value (enterprise value = market cap adjusted for net nebt). Regarding the second part of your question: Issuing new shares usually does not affect market cap in a significant way because the newly issued shares often result in lower share prices and dilution of the existing share holders shares." There are kind of two answers here: the practical reason an acquirer has to pay more for shares than their current trading price and the economic justification for the increase in price. Why must the acquirer must pay a premium as a practical matter?  Everyone has a different valuation of a company.  The current trading price is the lowest price that any holder of the stock is willing to sell a little bit of stock for and the highest that anyone is willing to buy a little bit for. However, Microsoft needs to buy a controlling share.  To do this on the open market they would need to buy all the shares from people who's personal valuation is low, and then a bunch from people whose valuation is higher and so on.  The act of buying that much stock would push the price up by buying all the shares from people who are really willing to sell.  Moreover, as they buy more and more, the remaining people increase their personal valuation so the price would really shoot up.  Acquirers avoid this situation by offering to buy a ton of stock at a substantially higher, single price. Why is Linkedin suddenly worth more than it was yesterday? Microsoft is expecting to be able to use its own infrastructure and tools to make more money with Linkedin than Linkedin would have before.  In other words, they believe that the Linkedin division of Microsoft after the merger will be worth more than Linkedin alone was before the merger.  This synergistic idea is the theoretical foundation for mergers in general and the main reason people use to argue for a higher price. You could also argue that by expressing an interest in Linkedin, Microsoft may be telling us something it knows about Linkedin's value that maybe we didn't realize before because we aren't as smart and informed as the people on Microsoft's board.  But since it's Microsoft that's doing the buying in this case, I'm going to go out on a limb and say this is not the main effect.  Given Microsoft's history, the idea that they buy expensive things because they have money to burn is more compelling than the idea that they have an insight into a company's value that we don't. "It means that the company earned 15 cents per share in the most recently reported quarter. Share price may or not be affected, depending on how buyers and sellers value the company. Just because profits ""jumped,"" does not mean the shares will follow suit. An increase in profits may have already been priced into the stock, or the market expected the increase in profit to be even higher. As the shareholder, you don't actually get any of these profits into your hands, unless the company pays out a portion of these profits as a dividend." When you buy shares, you are literally buying a share of the company.  You become a part-owner of it. Companies are not required to pay dividends in any given year.  It's up to them to decide each year how much to pay out. The value of the shares goes up and down depending on how much the markets consider the company is worth.  If the company is successful, the price of the shares goes up.  If it's unsuccessful, the price goes down.  You have no control over that.  If the company fails completely and goes bankrupt, then the shares are worthless. Dilution is where the company decides to sell more shares.  If they are being sold at market value, then you haven't really lost anything.  But if they are sold below cost (perhaps as an incentive to certain staff), then the value of the company per share is now less.  So your shares may be worth a bit less than they were.  You would get to vote at the AGM on such schemes.  But unless you own a significant proportion of the shares in the company, your vote will probably make no difference. In practice, you can't protect yourself.  Buying shares is a gamble.  All you can do is decide what to gamble on. It means $400m expected revenue, likely spread out over multiple years as it gets implemented, and not entirely guaranteed to happen as they still need to fulfill the contract. The impact on the stock price is complex - it should be positive, but nowhere close to a $400m increase in market cap. If the company is expected to routinely win such contracts, it may have no significant effect on the stock price, as it's already priced in - say, if analysts expect the company to win 1.2b contracts in this fiscal year, and now they've done 1/3 of that, as expected.