Brief concept about price movement of a particular stock [duplicate]
There isn't a formula like that, there is only the greed of other market participants, and you can try to predict how greedy those participants will be. If someone decided to place a sell order of 100,000 shares at $5, then you can buy an additional 100,000 shares at $5. In reality, people can infer that they might be the only ones trying to sell 100,000 shares right then, and raise the price so that they make more money. They will raise their sell order to $5.01, $5.02 or as high as they want, until people stop trying to buy their shares. It is just a non-stop auction, just like on ebay. It depends completely on the current order book for that security.  There is literally no telling how that buy order would move the price of a stock in general. The problem with predicting with accuracy what a stock price will do in any given situation is that there are two main factors that affect a stocks price. The first factor is based somewhat in math as it takes into account numbers such as supply and demand, earnings per share, expected earnings, book value, debt ratio and a wide variety of other numbers. You can compile all those numbers into a variety of formulas and come up with a rational estimate of what the stock should sell for. This is all well and good and if the market were entirely rational it would rarely make news because it would be predictable and boring. This is where our second factor throws a wrench in the works.  The second factor affecting stock price is emotional. There are many examples of people's emotions affecting stock price but if you would like a good example look up the price fluctuations of Apple  (AAPL) after their last couple earnings reports. Numerically their company looks good, their earnings were healthy, their EPS is below average yet their price fell following the report. Why is that?  There really isn't a rational reason for it, it is driven by the emotions behind unmet expectations. In a more general sense sometimes price goes down and people get scared and sell causing further decline, sometimes people get excited and see it as opportunity to buy in and the price stabilizes. It is much more difficult to anticipate the reaction the market will have to people's emotional whims which is why predicting stock price with accuracy is near impossible.  As a thought along the same line ask yourself this question; if the stock market were entirely rational and price could be predicted with accuracy why is there such a wide range of available strike prices available in the options market?  It seems that if stock price could be predicted with anything remotely reassembling accuracy the options market need a much smaller selection of available strike prices.
You'd need millions of dollars to trade the number of shares it would take to profit from these penny variations.  What you bring up here is the way high frequency firms front-run trades and profit on these pennies. Say you have a trade commission of $5.  Every time you buy you pay $5, every time you sell you pay $5.  So you need a gain in excess of $10, a 10% gain on $100.  Now if you wanted to trade on a penny movement from $100 to $100.01, you need to have bought 1,000 shares totaling $100,000 for the $0.01 price movement to cover your commission costs.  If you had $1,000,000 to put at risk, that $0.01 price movement would net you $90 after commission, $10,000,000 would have made you $990.  You need much larger gains at the retail level because commissions will equate to a significant percentage of the money you're investing. Very large trading entities have much different arrangements and costs with the exchanges.  They might not pay a fee on each transaction but something that more closely resembles a subscription fee, and costs something that more closely resembles a house. Now to your point, catching these price movements and profiting.  The way high frequency trading firms purportedly make money relates to having a very low latency network connection to a particular exchange.  Their very low latency/very fast network connection lets them see orders and transact orders before other parties.   Say some stock has an ask at $101 x 1,000 shares.  The next depth is $101.10.  You see a market buy order come in for 1,000 shares and place a buy order for 1,000 shares at $101 which hits the exchange first, then immediately place a sell order at $101.09, changing the ask from $101.00 to $101.09 and selling in to the market order for a gain of $0.09 per share. "The argument you are making here is similar to the problem I have with the stronger forms of the efficient market hypothesis.  That is if the market already has incorporated all of the information about the correct prices, then there's no reason to question any prices and then the prices never change.  However, the mechanism through which the market incorporates this information is via the actors buying an selling based on what they see as the market being incorrect. The most basic concept of this problem (I think) starts with the idea that every investor is passive and they simply buy the market as one basket.  So every paycheck, the index fund buys some more stock in the market in a completely static way.  This means the demand for each stock is the same.  No one is paying attention to the actual companies' performance so a poor performer's stock price never moves.  The same for the high performer.  The only thing moving prices is demand but that's always up at a more or less constant rate. This is a topic that has a lot of discussion lately in financial circles.  Here are two articles about this topic but I'm not convinced the author is completely serious hence the ""worst-case scenario"" title. These are interesting reads but again, take this with a grain of salt.  You should follow the links in the articles because they give a more nuanced understanding of each potential issue.  One thing that's important is that the reality is nothing like what I outline above. One of the links in these articles that is interesting is the one that talks about how we now have more indexes than stocks on the US markets.  The writer points to this as a problem in the first article, but think for a moment why that is.  There are many different types of strategies that active managers follow in how they determine what goes in a fund based on different stock metrics.  If a stocks P/E ratio drops below a critical level, for example, a number of indexes are going to sell it.  Some might buy it.  It's up to the investors (you and me) to pick which of these strategies we believe in. Another thing to consider is that active managers are losing their clients to the passive funds.  They have a vested interest in attacking passive management." "It is important to first understand that true causation of share price may not relate to historical correlation. Just like with scientific experiments, correlation does not imply causation. But we use stock price correlation to attempt to infer causation, where it is reasonable to do so. And to do that you need to understand that prices change for many reasons; some company specific, some industry specific, some market specific. Companies in the same industry may correlate when that industry goes up or down; companies with the same market may correlate when that market goes up or down. In general, in most industries, it is reasonable to assume that competitor companies have stocks which strongly correlate (positively) with each-other to the extent that they do the same thing.  For a simple example, consider three resource companies: ""Oil Ltd."" [100% of its assets relate to Oil]; ""Oil and Iron Inc."" [50% of its value relates to Oil, 50% to Iron]; and ""Iron and Copper Ltd."" [50% of its value relates to Iron, 50% to Copper]. For each of these companies, there are many things which affect value, but one could naively simplify things by saying ""value of a resource company is defined by the expected future volume of goods mined/drilled * the expected resource price, less all fixed and variable costs"". So, one major thing that impacts resource companies is simply the current & projected price of those resources. This means that if the price of Oil goes up or down, it will partially affect the value of the two Oil companies above - but how much it affects each company will depend on the volume of Oil it drills, and the timeline that it expects to get that Oil. For example, maybe Oil and Iron Ltd. has no currently producing Oil rigs, but it has just made massive investments which expect to drill Oil in 2 years - and the market expects Oil prices to return to a high value in 2 years.  In that case, a drop in Oil would impact Oil Inc. severely, but perhaps it wouldn't impact Oil and Iron Ltd. as much. In this case, for the particular share price movement related to the price of Oil, the two companies would not be correlated. Iron and Copper Ltd. would be unaffected by the price of Oil [this is a simplification; Oil prices impact many areas of the economy], and therefore there would be no correlation at all between this company's shares. It is also likely that competitors face similar markets. If consumer spending goes down, then perhaps the stock of most consumer product companies would go down as well. There would be outliers, because specific companies may still succeed in a falling market, but in generally, there would be a lot of correlation between two companies with the same market.  In the case that you list, Sony vs Samsung, there would be some factors that correlate positively, and some that correlate negatively. A clean example would be Blackberry stock vs Apple stock - because Apple's success had specifically negative ramifications for Blackberry. And yet, other tech company competitors also succeeded in the same time period, meaning they did not correlate negatively with Apple." It seems that you're interested in an asset which you can hold that would go up when the gold price went down. It seems like a good place to start would be an index fund, which invests in the general stock market. When the gold market falls, this would mainly affect gold mining companies. These do not make up a sizable portion of any index fund, which is invested broadly in the market. Unfortunately, in order to act on this, you would also have to believe that the stock market was a good investment.   To test this theory, I looked at an ETF index fund which tracks the S&P 500, and compared it to an ETF which invests in gold.  I found that the daily price movements of the stock market were positively correlated with the price of gold. This result was statistically significant.  The weekly price movements of the stock market were also correlated with the price of gold. This result was also statistically significant.  When the holding period was stretched to one month, there was still a positive relationship between the stock market's price moves and the price of gold. This result was not statistically significant.  When the holding period was stretched to one year, there was a negative relationship between the price changes in the stock market and the price of gold.  This result was not statistically significant, either. There's only one real list that states what people think stock prices should be, and that's the stocks order book. That lists the prices at which stock owners are willing to buy stocks now, and the price that buyers are willing to pay.  A secondary measure is the corresponding options price. Anything else is just an opinion and not backed by money. That is called a 'volume chart'. There are many interactive charts available for the purpose. Here is clear example.  (just for demonstration but this is for India only) 1) Yahoo Finance 2) Google Finance 3) And many more Usually, the stock volume density is presented together (below it) with normal price vs time chart. Note: There is a friendly site about topics like this. Quant.stackexchange.com. Think of checking it out. "To a certain degree ""the only sure thing I know is the price I paid for the stock is the fair price at the time I buy it"" is absolutely right, by definition, and by the law of the free and efficient market and forces of supply and demand, freedom of public information about share price sensitive information, etc, etc, etc, and you've made a good point that eludes many investors I'd say. However, in practise, the market has many participants, and they will all be arriving at a different idea of what the ""fair price"" is by way of a slightly different analysis and slightly different information. In theory they all have the same information, but unfortunately in practise there is always some disparity. When one participant feels a stock is undervalued though the last thing they want to do is say so, instead they will start buying stock. They might feel it is undervalued by 20%, but that doesn't mean they'll keep buying and buying until it gets to 20%, they might push the price up just a little, then let the price drift down again, buy some more, relax, buy some more, etc. Over time the price will rise of course because the supply will become weaker, but even if the participant is correct about the 20% the price might have only risen 7% by the time they acquire all the stock they want given their risk models, market exposure and margin guidelines, etc, and it might be more than a year later before the price has actually risen to 20%, presumably because more and more other market participants have come to the same conclusion. The opposite can obviously also happen, a participant might dump stock it feels is over valued long before it hits the values it believes in. So right away you can see that pricing might not really reflect value, or ""fair price""." The first statement is talking about a sudden sharp increase in volume (double or more of average volume) with a sudden increase in price. In other words, there has been a last rush to buy the stock exhausting all the current bulls (buyers), so the bears (sellers) take over, at least temporarily. Whilst the second statement is talking about a gradual increase in volume as the price up trends (thus the use of a volume oscillator). In other words (in an uptrend), the bulls (buyers) are gradually increasing in numbers sending the price higher, and new buyers keep entering the market. (The opposite is the case for a down-trend).