Why do stocks gap up after a buyout is announced?
The price gaps up because the offer is for a price above the current price. Therefore people want to buy now before the price jumps to the offer level. Of course it does depend on the tone of the announcement,  which party is making the announcement, and are they announcing an offer or a deal. If the price is $10, and the offer is for $12; then the price may quickly jump. The early buyers will make the most quick money. They hope that the deal is done quickly, or if not the final price ends up higher.  There are risks. The company could reject the offer. The due diligence could expose a problem. The regulators could reject the deal based on anti-trust issues. The deal could take many months to complete. Or the final deal could be for shares in the new company.  The risks are one reason people sell after the deal/offer is announced. In other cases the seller finally is seeing a profit, or a smaller loss and wants out while they can. "The ""random walk"" that you describe reflects the nature of the information flow about the value of a stock.  If the flow is just little bits of relatively unimportant information (including information about the broader market and the investor pool), you will get small and seemingly random moves, which may look like a meander.  If an important bit of information comes out, like a merger, you will see a large and immediate move, which may not look as random. However, the idea that small moves are a meander of search and discovery and large moves are immediate agreements is incorrect.  Both small moves and large moves are instantaneous agreements about the value of a stock in the form of a demand/supply equilibrium.  As a rule, neither is predictable from the point of view of a single investor, but they are not actually random.  They look different from each other only because of the size of the movement, not because of an underlying difference in how the consensus price is reached."
There is a strategy called merger-arbitrage where you buy the stock of the acquired company when it sells for less than the final acquisition price. Usually the price will rise to about the acquisition price fairly rapidly after the merge is announced, so you have to move fast. The danger is that the merger gets called off (regulatory reasons, the acquired company board votes no) and you get left holding shares bought at a price higher than the price after the merger collapses. This is kind of an advanced strategy and a tough one to back test since each M&A deal is unique. Would you mind adding where that additional value comes from, if not from the losses of other investors?  You asked this in a comment, but it seems to be the key to the confusion.   Corporations generate money (profits, paid as dividends) from sales.  Sales trade products for money.  The creation of the product creates value.  A car is worth more than General Motors pays for its components and inputs, even including labor and overhead as inputs.  That's what profit is:  added value.  The dividend is the return that the stock owner gets for owning the stock.   This can be a bit confusing in the sense that some stocks don't pay dividends.  The theory is that the stock price is still based on the future dividends (or the liquidation price, which you could also consider a type of dividend).  But the current price is mostly based on the likelihood that the stock price will increase rather than any expected dividends during ownership of the stock.   A comment calls out the example of Berkshire Hathaway.  Berkshire Hathaway is a weird case.  It operates more like a mutual fund than a company.  As such, investors prefer that it reinvest its money rather than pay a dividend.  If investors want money from it, they sell shares to other investors.  But that still isn't really a zero sum game, as the stock increases in value over time.   There are other stocks that don't pay dividends.  For example, Digital Equipment Corporation went through its entire existence without ever paying a dividend.  It merged with Compaq, paying investors for owning the stock.   Overall, you can see this in that the stock market goes up on average.  It might have a few losing years, but pick a long enough time frame, and the market will increase during it.  If you sell a stock today, it's because you value the money more than the stock.  If it goes up tomorrow, that's the buyer's good luck.  If it goes down, the buyer's bad luck.  But it shouldn't matter to you.  You wanted money for something.  You received the money.   The increase in the stock market overall is an increase in value.  It is completely unrelated to trading losses.  Over time, trading gains outweigh trading losses for investors as a group.  Individual investors may depart from that, but the overall gain is added value.   If the only way to make gains in the stock market was for someone else to take a loss, then the stock market wouldn't be able to go up.  To view it as a zero sum game, we have to ignore the stocks themselves.  Then each transaction is a payment (loss) for one party and a receipt (gain) for the other.  But the stocks themselves do have value other than what we pay for them.  The net present value of of future payments (dividends, buyouts, etc.) has an intrinsic worth.  It's a risky worth.  Some stocks will turn out to be worthless, but on average the gains outweigh the losses. "Matt Levine:  &gt;Also, though, I found it hard to imagine that those Equifax executives were consciously insider trading. It would just be too dumb. Equifax's press release reporting the breach says that it ""discovered the unauthorized access on July 29 of this year and acted immediately to stop the intrusion,"" though it didn't announce it until yesterday because it was still investigating. The three executives filed Form 4s reporting sales on Aug. 1 and 2, days after the discovery. You could just about imagine them learning of the security breach, panicking, and selling everything -- except that they didn't sell everything. One sold about 4 percent of his stock holdings, another about 9 percent, another about 13 percent. Why do such comically obvious insider trading if you're only selling a small percentage of your stock? And indeed the company explained that these executives ""had no knowledge that an intrusion had occurred at the time."" I guess the time between ""tech person discovers a security breach"" and ""top executives discover it's a huge embarrassing crisis"" is more than a couple of days.  https://www.bloomberg.com/view/articles/2017-09-08/data-breaches-and-last-looks" "As /u/Im_In_You replied, you need a lot more capital if you're going to make a difference in your personal finances. Remember to only invest the money that you can risk losing; don't put your emergency savings in the stock market.  As for success, I replied with this to a snarky poster above:  &gt;I started investing with $15,000 in 2009, my first trade being to buy Ford around $2 before the other two got bailed out. That single trade put me in the six figures. I've followed that up with equally successful trades such as shorting Netflix when they announced their new pricing plan, buying Tesla when they first started selling the Model S, etc. So yeah, even benchmarked against the 2009 bottom of the S&amp;P500, I've had ""success.""  Although the professionals have access to far more information than I ever will, there is something to be said for being able to predict major trends. After all, the stock will either go up or down. Even with all the data in the world, your only options are to either go long or short. You have a 50-50 chance of beating the hedge fund crowd. Admittedly, very few people will have the same returns I've had over the past ~5 years." There's an odd anomaly that often occurs with shares acquired through company plans via ESPP or option purchase. The general situation is that the share value above strike price or grant price may become ordinary income, but a sale below the price at day the shares are valued is a capital loss.  e.g. in an ESPP offering, I have a $10 purchase price, but at the end of the offering, the shares are valued at $100. Unless I hold the shares for an additional year, the sale price contains ordinary W2 income. So, if I see the shares falling and sell for $50, I have a tax bill for $90 of W2 income, but a $50 capital loss. Tax is due on $90 (and for 1K shares, $90,000 which can be a $30K hit) but that $50K loss can only be applied to cap gains, or $3K/yr of income.  In the dotcom bubble, there were many people who had million dollar tax bills and the value of the money netted from the sale couldn't even cover the taxes. And $1M in losses would take 300 years at $3K/yr.  The above is one reason the lockup date expiration is why shares get sold. And one can probably profit on the bigger companies stock.  Edit - see Yelp down 3% following expiration of 180 day IPO lock-up period, for similar situation. If you look at a trade grid you can see how this happens. If there are enough bids to cover all shares currently on the sell side at a certain price, those shares will be bought and increased price quotes will be shown for the bids and ask. If there are enough bids to cover this price, those will get bought and higher prices will be shown and this process will repeat until the sell side has more power than the buy side. It seems like this process is going on all day long with momentum either on the upside or downside. But I think that much of this bidding and selling is automatic and is being done by large trading firms and high tech computers. I also feel that many of these bids and asks are already programmed to appear once there is a price change. So once one price gets bought, computers will put in higher bids to take over asks. It's like a virtual war between trading firms and their computers. When more money is on the buy side the stock will go up, and vice versa. I sort of feel like this high-frequency trading is detrimental to the markets and doesn't really give everyone a fair shot. Retail investors do not have the resources and knowledge in order to do this sort of high frequency trading. It also seems to go against certain free market principles in my opinion. Selling stock means selling a portion of ownership in your company.  Any time you issue stock, you give up some control, unless you're issuing non-voting stock, and even non-voting stock owns a portion of the company. Thus, issuing (voting) shares means either the current shareholders reduce their proportion of owernship, or the company reissues stock it held back from a previous offering (in which case it no longer has that stock available to issue and thus has less ability to raise funds in the future).  From Investopedia, for exmaple: Secondary offerings in which new shares are underwritten and sold dilute the ownership position of stockholders who own shares that were issued in the IPO. Of course, sometimes a secondary offering is more akin to Mark Zuckerberg selling some shares of Facebook to allow him to diversify his holdings - the original owner(s) sell a portion of their holdings off.  That does not dilute the ownership stake of others, but does reduce their share of course. You also give up some rights to dividends etc., even if you issue non-voting stock; of course that is factored into the price presumably (either the actual dividend or the prospect of eventually getting a dividend).  And hopefully more growth leads to more dividends, though that's only true if the company can actually make good use of the incoming funds. That last part is somewhat important.  A company that has a good use for new funds should raise more funds, because it will turn those $100 to $150 or $200 for everyone, including the current owners.  But a company that doesn't have a particular use for more money would be wasting those funds, and probably not earning back that full value for everyone. The impact on stock price of course is also a major factor and not one to discount; even a company issuing non-voting stock has a fiduciary responsibility to act in the interest of those non-voting shareholders, and so should not excessively dilute their value. In principle, the stock price should see no change in the days leading up to an earnings announcement, and then at the moment of the announcement, the stock price should move in the direction of the earnings surprise (relative to the market's belief of what earnings were going to be). In practice, stock prices tend to drift a little in the direction of the surprise shortly before the announcement and the associated price jump. This could be because smart investors were able to replicate the computations to predict the announcement or because information gets illegally leaked ahead of the announcement.  So I guess your bullet point B is a likely scenario. Note that hedging activity in the options market will not affect stock price one way or another.  Options transfer risk from one party to another but net to zero.  Intense hedging activity may be able to push up the price of options (increasing the implied volatility), but it shouldn't affect the price of a stock one way or the other. For this reason, bullet point A is not the case. Note that price behavior after the announcement is also interesting: it seems to take some time to reach the correct price instead of jumping directly to it as economists would predict.   This phenomenon is known as post earnings announcement drift.