How does a stock operate when it is listed between two exchanges?
Say a stock is listed in Nasdaq, and the same company has a stock listed in Tsx. Does the Nasdaq price affect the Tsx price as trading commences? Not directly. Basically, an exchange is a market, and the price is defined only by supply and demand in that market. However, any substantial price differential for a commodity traded in multiple market creates an arbitrage opportunity, and there are many traders whose job it is exactly to find and use such opportunities. Their activity in turn has the effect of reducing the price differentials to the point where transaction costs make them unprofitable. With high-frequency traders around, the time for a price differential to disappear is nowadays measured in milliseconds. If a trader buys from one exchange, will it affect the price of the other? Only through the mechanism mentioned above.  Are there any benefits to being listed in two exchanges? It increases the liquidity of a stock.
Firstly, you mean resistance not support, as a support is below the current price and resistance is above the price. Secondly using a MA as support or resistance would mean that that support or resistance level would move up or down as the price moved up or down and would not be static at $25. Generally stocks will range trade more often than they will be trending (either up or down), so a stock can be range trading between a support and resistance levels for months and even years, and usually the longer it range trades for, the bigger the outbreak (either up or down) will be when it does happen. Using a MA (especially shorter dated ones) as support or resistance (or as a up or down trend line) works better when a stock is already trending up or down. When a stock is moving sideways it will tend to keep crossing above and below the MA, and you will be whipsawed if you try to use them as your trigger for entry in these situations. Compare the two charts below:  In the first chart the stock is up-trending for over 6 months and the 50d EMA is being used as a support or up-trending line. As long as the price does not break through and close under the 50d EMA then the uptrend continues. You could use this EMA line as a means of entering the stock when prices move towards the EMA and bounce off it back up again. Or you could use it as your stop loss level, so if price closes below the EMA line you would sell your position.  In the second chart, the stock has been range trading between the support line at about $21.80 and the resistance line at about $25.50 for 10 months. In this case the price has been moving above and below the 50d EMA during these 10 months and you may have been whipsawed many times if you were trading each break above or below the 50d EMA. A better strategy here would be to buy the stock as it approached the support line and bounces up off it and then close and reverse your position (go short) when the price approached the resistance line and bounces down off it.  Edit: When range trading you would have your stops just below the support line when going long and just above the resistance line when going short, that way if it does break through support or resistance and starts trending you will be covered. So this shows that different strategies should be used when a stock is trending to when it is range trading. MAs are better used as entry signal during an established uptrend or downtrend than when a stock is range trading. If a company's shares trade in multiple exchanges, the prices in every exchange are very near to each other, otherwise you could earn money by doing arbitrage deals (buying in one, selling in the other) - and people do that once it becomes worth it. Which stock exchange you use is more a convenience for the buyer/seller - many investment banks offer only something local/near, and you have to go to specific investment banks to use other exchanges. For example, in Germany, it is easy to deal in Frankfurt, but if you want to trade at the the NASDAQ, you have to run around and find a bank that offers it, and you probably have to pay extra for it. In the USA, most investment banks offer NASDAQ, but if you want to trade in Frankfurt, you will have run around for an international company that offers that. As a stock owner/buyer, you can sell/buy your shares on any stock exchange where the company is listed (again, assuming your investment broker supports it). So you can buy in Frankfurt and sell in Tokyo seconds later, as nothing needs to be physically moved. Companies that are listed in multiple stock exchangs are typically large, and offer this to make trading their shares easier for a larger part of the world. Considering your 'theoretical buy all shares' - the shares are not located in the exchanges, they are in the hands of the owners, and not all are for sale, for various reasons. The owners decide if and when they want them offered for sale, and they also decide which stock exchange they offer them on; so you would need to go to all exchanges to buy them all. However, if you raise your offer price in one exchange only slightly, someone will see the arbitrage and buy them in the other locations and offer them to you in your stock exchange; in other words, for a small fee the shares will come to you. But again, most shares are typically not for sale. It's the same as trying to buy all Chevy Tahoes - even if you had the money, most owners wouldn't know or care about you. You would have to go around and contact every single one and convince them to sell. You pointed out that HFT does not create ipods are mine minerals.  Neither does human trading. HFT is a proxy for human trading.  Although the computer is executing trades automatically based on an algorithm, it is still using money from a human being's account so the trading is still being done with someone's money. Fast execution of trades is desirable in exchanges.  Imagine two exchanges:  One only executes trades once a month, the other executes trades once a week.  Which exchange would be more desirable?  The exchange that trades once a week.  Why?  Because if I'm holding a stock that I would like to sell, I want to sell it now - not a month from now.  Same reason for buying.  This concept works all the way down to seconds and fractions of seconds. The issue with HFT, however, is there are cases where the market goes against the HFT algorithm and the algorithm continues to execute trades driving prices up or down by large amounts in the matter of minutes or even seconds. The exchange frequently cancels these trades which only encourages more aggressive HFT trading since HFT traders can have their losses cancelled.  This is a privilege that LFTs (low frequency traders) do not receive.  This is a valid criticism of HFTs. A short list of such cancelled trades: 8/26/2010: Nasdaq cancels trades of CORE stock 10/4/2010: Nasdaq cancels trades of CENX stock 10/15/2010: NYSE cancels trades of PAY stock 10/18/2010: NYSE cancels $500 million worth of SPY trades 5/18/2011: NYSE cancels 15,900 trades of BEE.PR.C 6/21/2011: Nasdaq cancels CNTY trades 12/2/2011: London Metals Exchange cancel trades of copper "A falling exchange rate is an indication of falling confidence in a currency.  Countries like Iran or Venezuela, with a managed exchange rate, set their exchange rates at a higher value than the market accepts. Such market expectations may be influenced by poor government management, interventions into markets (such as nationalising businesses) or general instability / scarcity. The governments act to manage that uncertainty by limiting the availability of foreign exchange and pegging the exchange rate.   Since there is an inadequate supply of trusted foreign currency people turn to informal exchanges in order to hedge their currency risk.  This creates a negative feedback loop.  People in government who have access to foreign exchange start to trade on informal markets, pocketing the difference in the official and unofficial rates.  The increasing gap between the two rates drives increasing informal market exchange and can result in speculative bubbles. Driving instability (or economic contradiction) is that the massive and increasing difference between the official and market exchange rates becomes a powerful form of rent for government officials. This drives further state-led rent-seeking behaviour and causes the economy to become even more unstable. If you're interested in a more formal academic study of how such parallel markets in currency arise, ""Zimbabwe’s Black Market for Foreign Exchange"" by Albert Makochekanwa at the University of Pretoria is a useful source." "You might consider learning how the ""matching"" or ""pairing"" system in the market operates.  The actual exchange only happens when both a buyer and a seller overlap their respect quotes.   Sometimes orders ""go to market"" for a particular volume.  Eg get me 10,000 Microsoft shares now.  which means that the price starts at the current lowest seller, and works up the price list until the volume is met.  Like all market it trades, it has it's advantages, and it's dangers.  If you are confident Microsoft is going to bull, you want those shares now, confident you'll recoup the cost.  Where if you put in a priced order, you might get only none or some shares. Same as when you sell.  If you see the price (which is the price of the last completed ""successful"" trade.  and think ""I'm going to sell 1000 shares"". then you give the order to the market (or broker), and then the same as what happened as before.  the highest bidder gets as much as they asked for, if there's still shares left over, they go to the next bidder, and so on down the price... and the last completed ""successful"" trade is when your last sale is made at the lowest price of your batch. If you're selling, and selling 100,000 shares. And the highest bidder wants 1,000,000 shares you'll only see the price drop to that guys bid.  Why will it drop (off the quoted price?).  Because the quoted price is the LAST sale, clearly if there's someone still with an open bid on the market...then either he wants more shares than were available (the price stays same), or his bid wasn't as high as the last bid (so when you sale goes through, it will be at the price he's offering).   Which is why being able to see the price queues is important on large traders. It is also why it can be important put stops and limits on your trades, een through you can still get gapped if you're unlucky.  However putting prices (""Open Orders"" vs ""(at)Market Orders"") can mean that you're sitting there waiting for a bounce/spike while the action is all going on without you). safer but not as much gain (maybe ;) ) that's the excitement of the market, for every option there's advantages...and risks... (eg missing out) There are also issues with stock movement, shadowing, and stop hunting, which can influence the price. But the stuff in the long paragraphs is the technical reasons." Thanks to the other answers, I now know what to google for. Frankfurt Stock Exchange: http://en.boerse-frankfurt.de/equities/newissues London Stock Exchange: http://www.londonstockexchange.com/statistics/new-issues-further-issues/new-issues-further-issues.htm As far as I know, with ADRs you're essentially trading by proxy -- a depository bank is holding the actual stock certificate, and must provide you with the actual stock on demand. The one thing that is different is that in the event that the ADR is terminated (which sometimes happens with mergers), you have a limited period of time to sell the shares -- otherwise, you get the actual foreign stock that you may or may not be able to trade without transferring to a different broker. You can execute block trades on the options market and get exercised for shares to create a very large position in Energy Transfer Partners LP without moving the stock market. You can then place limit sell orders, after selling directly into the market and keep an overhang of low priced shares (the technical analysis traders won't know what you specifically are doing, and will call this 'resistance'). If you hit nice even numbers (multiples of 5, multiples of 10) with your sell orders, you can exacerbate selling as many market participants will have their own stop loss orders at those numbers, causing other people to sell at lower and lower prices automatically, and simultaneously keep your massive ask in effect. If your position is bigger than the demand then you can keep a stock lower. The secondary market doesn't inherently affect a company in any way. But many companies have borrowed against the price of their shares, and if you get the share price low enough they can get suddenly margin called and be unable to service their existing debt. You will also lose a lot of money doing this, so you can also buy puts along the way or attempt to execute a collar to lower your own losses. The collar strategy is nice because it is unlikely that other traders and analysts will notice what you are doing, since there are calls, puts and share orders involved in creating it. One person may notice the block trade for the calls initially, but nobody will notice it is part of a larger strategy with multiple legs. With the share position, you may also be able to vote on some things, but that solely depends on the conditions of the shares.