What is the relationship between the earnings of a company and its stock price?
In general over the longer term this is true, as a company whom continuously increases earnings year after year will generally continue to increase its share price year after year. However, many times when a company announces increased earning and profits, the share price can actually go down in the short term. This can be due to the market, for example, expecting a 20% increase but the company only announcing a 10% increase. So the price can initially go down. The market could already have priced in a higher increase in the lead up to the announcement, and when the announcement is made it actually disapoints the market, so the share price can go down instead of up. I have heard that people say the greater earning means greater   intrinsic value of the company. Then, the stock price is largely based   on the intrinsic value. So increasing intrinsic value due to   increasing earning will lead to increasing stock price. Does this make   sense ? Yes though it may be worth dissecting portions here. As a company generates earnings, it has various choices for what it can do with that money. It can distribute some to shareholders in the form of dividends or re-invest to generate more earnings. What you're discussing in the first part is those earnings that could be used to increase the perceived value of the company. However, there can be more than a few interpretations of how to compute a company's intrinsic value and this is how one can have opinions ranging from companies being overvalued to undervalued overall. Of Mines, Forests, and Impatience would be an article giving examples that make things a bit more complex. Consider how would you evaluate a mine, a forest or a farm where each gives a different structure to the cash flow? This could be useful in running the numbers here. You would think that share prices is just a reflection of how well the company is doing but that is not always the case. Sometimes it reflects the investor confidence in the company more than the mere performance. So for instance if some oil company causes some natural disaster by letting one of there oil tankers crash into a coral reef then investor confidence my take a big hit and share prices my fall even if the bottom line of the company was not all that effected.
"Stock returns cannot be evaluated on its own. You need to take into account inflation and the return of other investment vehicles. Over the long run, you want to earn more than your peers (ie inflation), or lose less than them. Stock lets you buy into the profits of a company managed by others. So the fundamental question is ""do those company managers make better decision than average person?"" Of course there are times when they make awful decisions (eg just before dotcom bubble), and sometimes the best decision is to close the business. But overall those people are much better educated, have higher IQ, more resourceful, etc, and so over long time and across all the companies, this is correct and hence the stock market premium." "You could not have two stocks both at $40, both with P/E 2, but one an EPS of $5 and the other $10.  EPS = Earnings Per Share P/E = Price per share/Earnings Per Share So, in your example, the stock with EPS of $5 has a P/E of 8, and the stock with an EPS of $10 has a P/E of 4.  So no, it's not valid way of looking at things, because your understanding of EPS and P/E is incorrect. Update: Ok, with that fixed, I think I understand your question better. This isn't a valid way of looking at P/E. You nailed one problem yourself at the end of the post: The tricky part is that you have to assume certain values remain   constant, I suppose But besides that, it still doesn't work. It seems to make sense in the context of investor psychology: if a stock is ""supposed to"" trade at a low P/E, like a utility, that it would stay at that low P/E, and thus a $1 worth of EPS increase would result in lower $$ price increase than a stock that was ""supposed to"" have a high P/E. And that would be true. But let's game it out: Scenario Say you have two stocks, ABC and XYZ. Both have $5 EPS. ABC is a utility, so it has a low P/E of 5, and thus trades at $25/share. XYZ is a high flying tech company, so it has a P/E of 10, thus trading at $50/share. If both companies increase their EPS by $1, to $6, and the P/Es remain the same, that means company ABC rises to $30, and company XYZ rises to $60. Hey! One went up $5, and the other $10, twice as much! That means XYZ was the better investment, right? Nope. You see, shares are not tokens, and you don't get an identical, arbitrary number of them. You make an investment, and that's in dollars. So, say you'd invested $1,000 in each. $1,000 in ABC buys you 40 shares. $1,000 in XYZ buys you 20 shares. Their EPS adds that buck, the shares rise to maintain P/E, and you have: ABC: $6 EPS at P/E 5 = $30/share. Position value = 40 shares x $30/share = $1,200 XYZ: $6 EPS at P/E 10 = $60/share. Position value = 20 shares x $60/share = $1,200 They both make you the exact same 20% profit. It makes sense when you think about it this way: a 20% increase in EPS is going to give you a 20% increase in price if the P/E is to remain constant. It doesn't matter what the dollar amount of the EPS or the share price is." A company's Return on Equity (ROE) is its net income divided by its shareholder's equity.  The shareholder's equity is the difference between total assets and total liabilities, and is not dependent on the stock price. What it takes to have a ROE over 100% is to have the income be greater than the equity.  This might happen for a variety of reasons, but one way a high ROE happens is if the shareholder's equity (the divisor) is small, which can occur if past losses have eroded the company's capital (the original invested cash and retained earnings).  If the equity has become a small value, the income for some period might exceed it, and so the ROE would be over 100%. Operating margin is not closely related to ROE.  Although operating income is related to net income, to calculate the margin you divide by sales, which is completely unrelated to shareholder's equity.  So there is no relationship with ROE to be expected.  Operating margin is primarily dependent on market conditions, and can be substantially different in different industries. Market price of a stock typically trades in a range of Price/Earnings Ratio (P/E ratio). Or in other words, price of a stock = Earnings * P/E ratio Because of this direct proportionality of stock price with earnings, stock prices move in tandem with earnings. Prices can go up or down for a variety of reasons. If interest rates decline typically every stock goes up, and vice versa. Ultimately, there are two main value-related factors to a price of a stock: the dividends the company may issue or the payoff in the event the company is bought by someone else. Any dividend paid will give concrete value to a stock. For example, imagine a company has shares selling at $1.00 and they announce that they will pay a dividend at the end of the year of $1.00 per share. If their claim is believable then the stock is practically FREE at $1.00 a share, so in all likelihood the stock will go up a lot, just on the basis of the dividend alone. If a company is bought by another, they need to buy at least a majority of the shares, and in some cases all the shares. Since the price the buyer will be willing to pay for the company is related to its potential future income for the buyer, the more profitable the company is, the more a buyer will be willing to pay and hence the greater the value of the stock. "It's been said before, but to repeat succinctly, a company's current share price is no more or less than what ""the market"" thinks that share is worth, as measured by the price at which the shares are being bought and sold. As such, a lot of things can affect that price, some of them material, others ethereal. A common reason to own stock is to share the profits of the company; by owning 1 share out of 1 million shares outstanding, you are entitled to 1/1000000 of that company's quarterly profits (if any). These are paid out as dividends. Two key measurements are based on these dividend payments; the first is ""earnings per share"", which is the company's stated quarterly profits, divided by outstanding shares, with the second being the ""price-earnings ratio"" which is the current price of the stock divided by its EPS. Your expected ""yield"" on this stock is more or less the inverse of this number; if a company has a P/E ratio of 20, then all things being equal, if you invest $100 in this stock you can expect a return of $5, or 5% (1/20). As such, changes in the expected earnings per share can cause the share price to rise or fall to maintain a P/E ratio that the pool of buyers are willing to tolerate. News that a company might miss its profit expectations, due to a decrease in consumer demand, an increase in raw materials costs, labor, financing, or any of a multitude of things that industry analysts watch, can cause the stock price to drop sharply as people look for better investments with higher yields. However, a large P/E ratio is not necessarily a bad thing, especially for a large stable company. That stability means the company is better able to weather economic problems, and thus it is a lower risk. Now, not all companies issue dividends. Apple is probably the most well-known example. The company simply retains all its earnings to reinvest in itself. This is typically the strategy of a smaller start-up; whether they're making good money or not, they typically want to keep what they make so they can keep growing, and the shareholders are usually fine with that. Why? Well, because there's more than one way to value a company, and more than one way to look at a stock. Owning one share of a stock can be seen quite literally as owning a share of that company. The share can then be valued as a fraction of the company's total assets.  Sounds simple, but it isn't, because not every asset the company owns has a line in the financial statements. A company's brand name, for instance, has no tangible value, and yet it is probably the most valuable single thing Apple owns. Similarly, intellectual property doesn't have a ""book value"" on a company's balance sheet, but again, these are huge contributors to the success and profitability of a company like Apple; the company is viewed as a center of innovation, and if it were not doing any innovating, it would very quickly be seen as a middleman for some other company's ideas and products. A company can't sustain that position for long even if it's raking in the money in the meantime. Overall, the value of a company is generally a combination of these two things; by owning a portion of stock, you own a piece of the company's assets, and also claim a piece of their profits. A large company with a lot of material assets and very little debt can be highly valued based solely on the sum of its parts, even if profits are lagging. Conversely, a company more or less operating out of a storage unit can have a patent on the cure for cancer, and be shoveling money into their coffers with bulldozers." Besides overnight news events and auction mechanisms there is a more fundamental reason the price of a stock is always moving.  Theoretically the stock price will move slightly even in the unlikely scenario that absolutely nothing of interest happens during the entire night.  Let me go into that in some more detail: Stock valuation using Discounted Cash FLow One of the fundamental reasons that stock value is constantly changing is because underneath every stock there is a company that expects to make some kind of profit or loss in the future. We have to go into the fundamentals of stock value to understand why this is important: One popular way to determine the value of a stock is by looking into the future and summing up all the earnings (or cashflows) it has yet to produce. You have to reduce each amount by a certain factor that gets larger for payments that are farther into the future. Think of it this way: a dollar in hand now is better than a dollar that you get tomorrow. This method of valuation is called Discounted Cash Flow (abbr. DCF; see the wikipedia article on DCF) Time's effect on stock value Now take the Close price C, and the open price O. Let's assume that since there has been no news, the expectations for future earnings are the same for C and O. Remember that the discounting factor for these earnings is dependent on the time until the cashflow occurs? For O, this time is slightly shorter than for C, and therefore the value will be slightly higher (or lower, when the company is expected to incur losses). So now you can see that even without all the external forces that continuously push and pull on the stock price, a stock still changes in value over time. Hope this helps. No.  Revenue is the company's gross income.  The stock price has no contribution to the company's income.  The stock price may be affected when the company's income deviates from what it was expected to be. If the company reported a loss at the previous quarter when the stock what at say $20/share, and now just before the company's next quarterly report, the stock trades around $10/share. There is a misunderstanding here, the company doesn't sell stock, they sell products (or services). Stock/share traded at equity market. Here is the illustration/chronology to give you better insight:   Now addressing the question What if the stock's price change? Let say, Its drop from $10 to $1 Is it affect XYZ revenue ? No why? because XYZ selling ads not their stocks the formula for revenue revenue = products (in this case: ads) * quantity the equation doesn't involve capital (stock's purchasing) "You can think of the situation as a kind of Nash equilibrium.  If ""the market"" values stock based on the value of the company, then from an individual point of view it makes sense to value stock the same way. As an illustration, imagine that stock prices were associated with the amount of precipitation at the company's location, rather than the assets of the company.  In this imaginary stock market, it would not benefit you to buy and sell stock according to the company's value.  Instead, you would profit most from buying and selling according to the weather, like everyone else.  (Whether this system — or the current one — would be stable in the long-term is another matter entirely.)" Most of stock trading occurs on what is called a secondary market. For example, Microsoft is traded on NASDAQ, which is a stock exchange. An analogy that can be made is that of selling a used car. When you sell a used car to a third person, the maker of your car is unaffected by this transaction and the same goes for stock trading. Still within the same analogy, when the car is first sold, money goes directly to the maker (actually more complicated than that but good enough for our purposes). In the case of stock trading, this is called an Initial Public Offering (IPO) / Seasoned Public Offering (SPO), for most purposes. What this means is that a drop of value on a secondary market does not directly affect earning potential. Let me add some nuance to this. Say this drop from 20$ to 10$ is permanent and this company needs to finance itself through equity (stock) in the future. It is likely that it would not be able to obtain as much financing in this matter and would either 1) have to rely more on debt and raise its cost of capital or 2) obtain less financing overall. This could potentially affect earnings through less cash available from financing. One last note: in any case, financing does not affect earnings except through cost of capital (i.e. interest paid) because it is neither revenue nor expense. Financing obtained from debt increases assets (cash) and liabilities (debt) and financing obtained from stock issuance increases assets (cash) and shareholder equity. "Check your math... ""two stocks, both with a P/E of 2 trading at $40 per share lets say, and one has an EPS of 5 whereas the other has an EPS of 10 is the latter a better purchase?"" If a stock has P/E of 2 and  price of $40 it has an EPS of $20. Not $10. Not $5." "If you are looking for numerical metrics I think the following are popular: Price/Earnings (P/E) - You mentioned this very popular one in your question.  There are different P/E ratios - forward (essentially an estimate of future earnings by management), trailing, etc..  I think of the P/E as a quick way to grade a company's income statement (i.e: How much does the stock cost verusus the amount of earnings being generated on a per share basis?). Some caution must be taken when looking at the P/E ratio.  Earnings can be ""massaged"" by the company.  Revenue can be moved between quarters, assets can be depreciated at different rates, residual value of assets can be adjusted, etc..  Knowing this, the P/E ratio alone doesn't help me determine whether or not a stock is cheap. In general, I think an affordable stock is one whose P/E is under 15. Price/Book - I look at the Price/Book as a quick way to grade a company's balance sheet.  The book value of a company is the amount of cash that would be left if everything the company owned was sold and all debts paid (i.e. the company's net worth).  The cash is then divided amoung the outstanding shares and the Price/Book can be computed.  If a company had a price/book under 1.0 then theoretically you could purchase the stock, the company could be liquidated, and you would end up with more money then what you paid for the stock. This ratio attempts to answer: ""How much does the stock cost based on the net worth of the company?"" Again, this ratio can be ""massaged"" by the company.  Asset values have to be estimated based on current market values (think about trying to determine how much a company's building is worth) unless, of course, mark-to-market is suspended.  This involves some estimating.  Again, I don't use this value alone in determing whether or not a stock is cheap. I consider a price/book value under 10 a good number.   Cash - I look at growth in the cash balance of a company as a way to grade a company's cash flow statement.  Is the cash account growing or not? As they say, ""Cash is King"".  This is one measurement that can not be ""massaged"" which is why I like it.  The P/E and Price/Book can be ""tuned"" but in the end the company cannot hide a shrinking cash balance. Return Ratios - Return on Equity is a measure of the amount of earnings being generated for a given amount of equity (ROE = earnings/(assets - liabilities)).  This attempts to measure how effective the company is at generating earnings with a given amount of equity.  There is also Return on Assets which measures earnings returns based on the company's assets. I tend to think an ROE over 15% is a good number. These measurements rely on a company accurately reporting its financial condition.  Remember, in the US companies are allowed to falsify accounting reports if approved by the government so be careful.  There are others who simply don't follow the rules and report whatever numbers they like without penalty. There are many others.  These are just a few of the more popular ones.  There are many other considerations to take into account as other posters have pointed out." It's safe to say that for mature companies, with profits that have been steady, and steadily growing, that a multiple of earnings can come into play. It's not identical between companies or even industries, but for consumer staples, for instance, you'll see a clustering around a certain P/E.  On the other hand, there are companies like FaceBook, 18 months ago, trading at 20, now at 70 with a 110 P/E. Did the guys valuing the stock simply get it wrong then or is it wrong now?  Contrast this with KO (Coca-cola) a 20 P/E and 3.2% dividend, PG (Proctor and Gamble) 21 P/E, 3% dividend.  Funny though, a $1M valuation for $50K in profit may be Shark ridiculous, but a $1B valuation on a $50M company with great prospects, i.e. a pipeline of new products in growing markets, is a steal.  Disclosure I have no positions in the mentioned stocks. My personal gold/metals target is 5.0% of my retirement portfolio. Right now I'm underweight because of the run up in gold/metals prices. (I haven't been selling, but as I add to retirement accounts, I haven't been buying gold so it is going below the 5% mark.) I arrived at this number after reading a lot of different sample portfolio allocations, and some books. Some people recommend what I consider crazy allocations: 25-50% in gold. From what I could figure out in terms of modern portfolio theory, holding some metal reduces your overall risk because it generally has a low correlation to equity markets. The problem with gold is that it is a lousy investment. It doesn't produce any income, and only has costs (storage, insurance, commissions to buy/sell, management of ETF if that's what you're using, etc). The only thing going for it is that it can be a hedge during tough times. In this case, when you rebalance, your gold will be high, you'll sell it, and buy the stocks that are down. (In theory -- assuming you stick to disciplined rebalancing.) So for me, 5% seemed to be enough to shave off a little overall risk without wasting too much expense on a hedge. (I don't go over this, and like I said, now I'm underweighted.)