Why some things are traded in an exchange while others are traded OTC
All securities must be registered with the SEC. Securities are defined as (1) The term “security” means any note, stock, treasury stock,   security future, security-based swap, bond, debenture, evidence of   indebtedness, certificate of interest or participation in any   profit-sharing agreement, collateral-trust certificate,   preorganization certificate or subscription, transferable share,   investment contract, voting-trust certificate, certificate of deposit   for a security, fractional undivided interest in oil, gas, or other   mineral rights, any put, call, straddle, option, or privilege on any   security, certificate of deposit, or group or index of securities   (including any interest therein or based on the value thereof), or any   put, call, straddle, option, or privilege entered into on a national   securities exchange relating to foreign currency, or, in general, any   interest or instrument commonly known as a “security”, or any   certificate of interest or participation in, temporary or interim   certificate for, receipt for, guarantee of, or warrant or right to   subscribe to or purchase, any of the foregoing. thus currencies are not defined as securities. While OTC transactions of securities is not outright forbidden, there are numerous regulations issued by the SEC as a result of the 1943 Exchange Act and others that make this difficult and/or costly. Many other securities are exempted from registration thus trade in a way that could be called OTC. Different countries have variances upon US law but are very similar. Any security could be traded OTC, but law prohibits it expressly or in such a way to make it relatively expensive; further, stock options are so tightly regulated that expiration dates, expiration intervals, strike intervals, and minimum ticks are all set by the authorities.
Academic research into ADRs seems to suggest that pairs-trading ADRs and their underlying shares reveals that there certainly are arbitrage opportunities, but that in most (but not all cases) such opportunities are quickly taken care of by the market. (See this article for the mexican case, the introduction has a list of other articles you could read on the subject). In some cases parity doesn't seem to be reached, which may have to do with transaction costs, the risk of transacting in a foreign market, as well as administrative & legal concerns that can affect the direct holder of a foreign share but don't impact the ADR holder (since those risks and costs are borne by the institution, which presumably has a better idea of how to manage such risks and costs). It's also worth pointing out that there are almost always arbitrage opportunities that get snapped up quickly: the law of one price doesn't apply for very short time-frames, just that if you're not an expert in that particular domain of the market, it might as well be a law since you won't see the arbitrage opportunities fast enough. That is to say, there are always opportunities for arbitrage with ADRs but chances are YOU won't be able to take advantage of it (In the Mexican case, the price divergence seems to have an average half-life of ~3 days). Some price divergence might be expected: ADR holders shouldn't be expected to know as much about the foreign market as the typical foreign share holder, and that uncertainty may also cause some divergence. There does seem to be some opportunity for arbitrage doing what you suggest in markets where it is not legally possible to short shares, but that likely is the value added from being able to short a share that belongs to a market where you can't do that. Just because it gets delisted from one of the big boards doesn't mean it can't trade over the counter.  For example GM went OTC under the ticker MTLQQ for a while.  That being said, just because the stock is trading over the counter doesn't mean it has any real long term value. Short answer: Liquidity. Well, you have to see it from an exchange's point of view.  Every contract they put up is a liability to them.  You have to allocate resources for the order book, the matching engine, the clearing, etc.  But only if the contract is actually trading they start earning (the big) money. Now for every new expiry they engage a long term commitment and it might take years for an option chain to be widely accepted (and hence before they're profitable).  Compare the volumes and open interests of big chains versus the weeklies and you'll find that weeklies can still be considered illiquid compared to their monthly cousins. Having said that, like many things, this is just a question of demand.  If there's a strong urge to trade July weeklies one day, there will be an option chain.  But, personally I think, as long as there are the summer doldrums there will be no rush to ask for Jul and Aug chains. Futures exchanges are essentially auction houses facilitating a two-way auction. While they provide a venue for buyers and sellers to come together and transact (be that a physical venue such as a pit at the CME or an electronic network such as Globex), they don't actively seek out or find buyers and sellers to pair them together. The exchanges enable this process through an order book. As a futures trader you may submit one of two types of order to an exchange: Market Order - this is sent to the exchange and is filled immediately by being paired with a limit order.   Limit Order - this is placed on the books of the exchange at the price you specify. If other participants enter opposing market orders at this price, then their market order will be paired with your limit order. In your example, trader B wishes to close his long position. To do this he may enter a market sell order, which will immediately close his position at the lowest possible buy limit price, or he may enter a limit sell order, specifying the price at or above which he is willing to sell. In the case of the limit order, he will only sell and successfully close his position if his order becomes the lowest sell order on the book. All this may be a lot easier to understand by looking at a visual image of an order book such as the one given in the explanation that I have published here: Stop Orders for Futures Finally, not that as far as the exchange is concerned, there is no difference between an order to open and an order to close a position. They're all just 'buy' or 'sell' orders. Whether they cause you to reduce/exit a position or increase/establish a position is relative to the position you currently hold; if you're flat a buy order establishes a new position, if you're short it closes your position and leaves you flat. "Nearly every country has its own exchange because so many countries have their own currency, and currency permeates every part of an exchange's business.   Generally, an exchange will support transaction and settlement only in local currency.  Securities (except those that explicitly enable FX trading) are denominated and will trade in a single currency-- you can only buy a share of IBM in U.S. dollars.  Securities trading always seeks to be a clean, frictionless, scalable process, and adding cross-currency translation to the mix would just complicate things.  So it's one exchange, one currency. In most countries, citizens and even businesses are largely restricted to having bank accounts in local currency.  There are various political reasons for this, but there it is:  it is difficult or impossible to open a domestic bank account in a foreign-denominated currency.  A public company headquartered in a given country will be required to publish financial statements in local currency, will be more likely to do business with the local citizenry and businesses in that currency, and so will likely look for investors from that same pool-- which generally means listing in local currency, which means on an exchange in that country. There are exceptions, of course.  Big multinationals do business all over the world, and many seek investors all over the world as well.  Mechanisms have been created to permit this (American Depositary Receipts or ADRs, for example).  But once again, cross-currency translation makes things more complicated, so ADRs and their like are only practical for very big international players. As to why there may be many exchanges in a single country, IMO Nick R has it right.  Read ""Flash Boys""; many market makers profit from trading between exchanges, and so have an interest in there being many of them.  And in the U.S., regulators have expressed an interest in ""innovation"" in the exchange space, and so permit them.  There is also an argument to be made against having a single ""Too Big To Fail"" exchange just like the argument for banks, but I wouldn't call that a ""reason"" for the current state of affairs." "There are basically two different markets for ADRs and ordinary shares. 1) The American market, 2) the ""local"" market. The following is not true for most stocks in ""developed"" markets. But it is often true that the American market (for ADRs) is far more liquid than the local market for ordinary shares of a developing country. For instance, there was a time when the ADRs of Telmex (Telefonos of Mexico) was the fifth most traded stock in the world, after Exxon (before its merger with Mobil), IBM, Microsoft, and A T&T, meaning that it was easy to trade with low fees on the NYSE. It was much harder and slower to buy the local shares of Telmex in Mexico, on the Mexican exchange. Also, the accompanying currency transactions were harder to execute with the ord, because you have to settle in local currency and pay an FX commission. With the ADR, the exchange rate is ""built"" into the (dollar) price, and you settle in dollars." The stock exchange here serves as a meeting place for current shareholders who want to sell their shares to someone else. This has nothing to do with liquidation, which is a transaction between the company and its shareholders. A company does not have to be listed on an exchange to make distributions to shareholders. "Changing my answer based on clarification in comments. It appears that some of the securities you mentioned, including GEAPP, are traded on what is colloquially known as the Grey Market. Grey Sheets, and also known as the ""Gray Market"" is another category of OTC stocks that is completely separate from Pink Sheets and the OTCBB.  From investopedia The grey market is an over-the-counter market where dealers may execute orders for preferred customers as well as provide support for a new issue before it is actually issued. This activity allows underwriters and the issuer to determine demand and price the securities accordingly before the IPO.  Some additional information on this type of stocks. (Source) Unlike other financial markets... No recent bid or ask quotes are available because no market makers share data or quote such stocks. There is no quoting system available to record and settle trades. All Grey sheet trading is moderated by a broker and done between consenting individuals at a price they agree on. The only documentation that can be publicly found regarding the trades is when the last trade took place. No SEC registration and little SEC regulation. Regulation of Grey Sheet stocks takes place mainly on a state level. Unlike Pink Sheets, these stocks have no SEC registration to possess a stock symbol or to possess shares or trade shares of that stock. Such penny stocks, similar to Pink Sheets, are not required to file SEC (Securities and Exchange Commission) financial and business reports. These stocks may not be solicited or advertised to the public unless a certain number of shares are qualified to be traded publicly under 504 of Regulation D. Extremely Illiquid. Gray sheet trading is infrequent, and for good reason... Difficult to trade, not advertised, difficult to follow the price, the least regulation possible, hard to find any information on the stock, very small market cap, little history, and most such stocks do not yet offer public shares. The lack of information (bids, history, financial reports) alone causes most investors to be very skeptical of Gray Sheets and avoid them altogether.  Gray Sheets are commonly associated with Initial public offering (IPO) stocks or start up companies or spin-off companies, even though not all are IPO's, start-ups or spin-offs. Grey Sheets is also Home to delisted stocks from other markets. Some stocks on this financial market were once traded on the NASDAQ, OTCBB, or the Pink Sheets but ran into serious misfortune - usually financial - and thus failed to meet the minimum requirements of the registered SEC filings and/or stock exchange regulations for a financial market. Such stocks were delisted or removed and may begin trading on the Grey Sheets.  So to answer your question, I think the cause of the wild swings is that:   Great question, BTW." "It's good to ask this question, because this is one of the fundamental dichotomies in market microstructure. At any time T for each product on a (typical) exchange there are two well-defined prices: At time T there is literally no person in the market who wants to sell below the ask, so all the people who are waiting to buy at the bid (or below) could very well be waiting there forever.  There's simply no guarantee that any seller will ever want to part with their product for a lesser price than they think it's worth. So if you want to buy the product at time T you have a tough choice to make: you get in line at the bid price, where there's no guarantee that your request will ever be filled, and you might never get your hands on the product you decide that owning the product right now is more valuable to you than (ask - bid) * quantity, so you tell the exchange that you're willing to buy at the ask price, and the exchange matches you with whichever seller is first in line Now, if you're in the market for the long term, the above choice is completely immaterial to you.  Who cares if you pay $10.00 * 1000 shares or $10.01 * 1000 shares when you plan to sell 30 years from now at $200 (or $200.01)? But if you're a day trader or anyone else with a very short time horizon, then this choice is extremely important: if the price is about to go up several cents and you got in line at the bid (and never got filled) then you missed out on some profit if you ""cross the spread"" to buy at the ask and then the price doesn't go up (or worse, goes down), you're screwed.  In order to get out of the position you'll have to cross the spread again and sell at at most the bid, meaning you've now paid the spread twice (plus transaction fees and regulatory fees) for nothing. (All of the above also applies in reverse for selling at the ask versus selling at the bid, but most people like to learn in terms of buying rather than selling.)" Yes, it does matter very much. There's a thing called fungible instruments. These are the instruments where it doesn't matter. E.g. most options I ever dealt with in the US are fungible no matter which US exchange you trade them on. A fungible instrument is an instrument where you buy 1 lot on exchange A, then sell 1 lot on exchange B, and as a result you have 0 lots.  With another instrument, you can buy 1 lot on exchange A, sell 1 lot on exchange B, and even tough they are the exact same thing, you now own 1, and owe 1 - they don't cancel each other out. Other than that, in different countries there are obviously different laws and regulations. For a small at home trader who just gambles for fun and isn't interested in negative positions (sell what you don't have), there isn't much of a difference . I think that's what the other answers are saying. While that sounds reasonable, it looks like most of the actual trading is done on the basis of changes rather than value.  At a guess, this is because computing the balance sheet anew with every change inhibits the speed with which transactions can be processed. Something to consider is that in the case of the company you chose, on the OTC market, that stock is thinly traded and with such low volume, it can be easy for it to fluctuate greatly to have trades occur.  This is why volume can matter for some people when it comes to buying shares. Some OTC stocks may have really low volume and thus may have bigger swings than other stocks that have higher volume. I don't quite understand the NYSE argument that the credit system helps NASDAQ undercut NYSE on pricing and force brokers to trade on NASDAQ. I thought if you were trading a stock listed on NASDAQ, you traded through them and if you were trading a stock listed on NYSE, you'd trade over there. The choice of exchange coming down to the stocks you want to trade more than anything. Are the exchanges also acting as endpoints on trades for securities listed on the other exchange? Many of the Bitcoin exchanges mimic stock exchanges, though they're much more rudimentary offering only simple buy/sell/cancel orders.  It's fairly normal for retail stock brokerage accounts to allow other sorts of more complex orders, where once a certain criteria is met, (the price falls below some $ threshold, or has a movement greater than some %) then your order is executed.  The space between the current buy order and the current sell order is the bid/ask spread, it's not really about timing.  Person X will buy at $100, person Y will sell at $102.  If both had a price set at $101, they would just transact.  Both parties think they can do a little bit better than the current offer.  The width of the bid/ask spread is not universal by any means.  The current highest buy order and the current lowest sell order, are both the current price.  The current quoted market price is generally the price of the last transaction, whether it's buy or sell. The Limit Order are matched based on amount and time. The orders are listed Highest to Lowest on the Buy Side. The orders are listed Lowest to Highest on the Sell Side. If there are 2 Sell orders for same amount the order which is first in time [fractions of milliseconds] is first.  The about is the example as to how the orders would look like on any exchange.  Now the highest price the buyer is ready to pay is 20.21 and the lowest price a seller is ready to sell for is 20.25. Hence there is no trade. Now if a new Buy order comes in at 20.25, it matches with the sell and the deal is made. If a new Buy order comes in at 20.30, it still matches at 20.25. Similarly if a Sell order come in at 20.21, it matches and a deal is made. If a Sell order come in at 20.11, it still matches 20.21.   Incase of market order, with the above example if there is a Buy order, it would match with the lowest sell order at 20.25, if there is not enough quantity , it would match the remaining quantity to the next highest at 20.31 and continue down. Similarly if there is a Sell market order, the it would match to the maximum a seller is ready to buy, ie 20.21, if there is not sufficient buy quantity at 20.21, it will match with next for 20.19   If say there are new buy order at 20.22 and sell orders at 20.24, these will sit first the the above queue to be matched. In your above example the Lowest Sell order was at 20.10 at time t1 and hence any buy order after time t1 for amount 20.10 or greater would match to this and the price would be 20.10. However if the Buy order was first ie at t1 there was a buy order for 20.21 and then at time later than t1, there is a sell order for say 20.10 [amount less than or equal to 20.21] it would match for 20.21. Essentially the market looks at who was the first to sell at lower price or who was the first to buy at higher price and then decide the trade.  Edit [To Clarify xyz]: Say if there is an Sell order at $10 Qty 100. There is a buyer who is willing to pay Max $20 and is looking for Qty 500. Your key assumption that the Buyer does not know the current SELL price of $10 is incorrect. Now there are multiple things, the Buyer knows the lowest Sell order is at $10, he can put a matching Buy order at $10 Qty 100, and say $11 Qty 100 etc. This is painful. Second, lets say he puts a Buy order at $10 Qty 100, by the time the order hits the system someone else has put the trade at $10 and his order is fulfilled. So this buyer has to keep looking at booking and keep making adjustments, if its a large order, it would be extremely difficult and frustrating for this Buyer. Hence the logic of giving preference. The later Buy order says ... The Max I can pay is $20, match eveything at the current price and get the required shares.