How are ADRs priced?
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.
"The case you are looking at is rather special, because the Chinese government for the longest time did not allow foreigners to invest in Chinese stocks. The ADRs explained in @DStanley's answer are a way around that restriction; recently there are some limited official ways,  In general, it is perfectly normal for a stock to appear on different exchanges, in different currencies, and it's all the ""real"" stock. Because remember: a stock exchange is really nothing more than a fancy place for people to buy and sell stocks. There is absolutely no reason why a specific stock should only be traded in one place. Companies that have decided to be publically tradeable generally want to be traded in as many exchanges as possible, because it makes the stock more liquid, which helps their shareholders. Individual exchanges have different requirements for a stock to be listed for trading there, some may even do it without the company's explicit approval." Some of the factors that will act on house prices are: There will likely be a recession in that country, which will lower incomes and probably lower housing prices. It will likely be harder to get credit in that country so that too will increase demand and depress demand for housing (cf the USA in 2010.) If Greece leaves the Euro, that will possibly depress future economic growth, through decreased trade and investment, and possibly decreased transfer payments. Eventually the budget will need to come back into balanced which also is likely to push down house prices. In some European countries (most famously Spain) there's been a lot of speculative building which is likely to hang over the market. Both countries have governance and mandate problems, and who knows how long or how much turmoil it will take to sort that out. Some of these factors may already be priced in, and perhaps prices are already near what will turn out to be the low. In the Euro zone you have the nearly unprecedented situation of the countries being very strongly tied into another currency, so the typical exchange-rate movements that played out in Argentina cannot act here.  A lot will depend on whether the countries are bailed out, or leave the Euro (and if so how), etc.  Typically inflation has been a knock-on effect of the exchange rate moves so it's hard to see if that will happen in Greece. Looking back from 2031, buying in southern Europe in 2011 may turn out to be a good investment.  But I don't think you could reasonably call it a safe defensive investment. It's still the purchase price or the price at which the shares are purchased or granted. This Investopedia article describes how the price is used for tax purposes: The amount that must be declared [for tax purposes] is determined by subtracting the original purchase or exercise price of the stock (which may be zero) from the fair market value of the stock as of the date that the stock becomes fully vested. Restricted stock awards are similar to stock options. The employer promises to grant the employee a certain number of shares upon the completion of the vesting schedule. The price at which the shares are purchased (or granted, if the price is zero) is the exercise price. "Think about moving the decimal point in a bunch of accounting software and price stickers. Think about getting confused, ""is that price in old yen or new yen?"" - not just immediately, but every time you hear a historical price figure. Think of the inconveniences. How many billions of yen would that cost the Japanese economy? It could be a lot. How many billions of yen would the Japanese economy save by enacting such a conversion? Because I doubt it's anywhere that much." Assuming the data you're referring to is this line: the difference might be related to the different exchanges on which the stock trades.  FINRA could be listing the reported volume from one exchange, while the NASDAQ data might be listing the volume on all exchanges. This is an important distinction because AAV is a Canadian company that is listed on the Toronto Stock Exchange and the NYSE. The Q at the end of the line stands for NASDAQ, according to FINRA's codebook for those data. My guess is that the FINRA data is only reporting the volume for the NASDAQ exchange and not the total volume for all exchanges (Toronto, NASDAQ, NYSE, etc.) while the data straight from NASDAQ, oddly enough, is reporting the total volume. However, FINRA could also face reporting discrepancies, since it's a regulatory body and therefore might not have the most up-to-date volume data that the various exchanges can access.  I don't know if it's related or not, but looking at the NASDAQ historical data, it looks like the volume on March 6, the day you're asking about, was much lower than the volume in most of the days immediately before or after it. For all I know, something might have happened that day concerning that particular stock or the market as a whole. I don't remember anything in particular, but you never know. You have to call Interactive Brokers for this. This is what you should do, they might even have a web chat. These are very broker specific idiosyncrasies, because although margin rules are standardized to an extent, when they start charging you for interest and giving you margin until settlement may not be standardized. I mean, I can call them and tell you what they said for the 100 rep. "Volume is measured in the number of shares traded in a given day, week, month, etc. This means that it's not necessarily a directly-comparable measure between stocks, as there's a large difference between 1 million shares traded of a $1 stock ($1 million total) and 1 million shares traded of a $1000 stock ($1 billion total). Volume as a number on its own is lacking in context; it often makes more sense to look at it as an overall dollar amount (as in the parentheses above) or as a fraction of the total number of shares in the marketplace. When you see a price quoted for a particular ticker symbol, whether online, or on TV, or elsewhere, that price is typically the price of the last trade that executed for that security. A good proxy for the current fair price of an asset is what someone else paid for it in the recent past (as long as it wasn't too long ago!). So, when you see a quote labeled ""15.5K @ $60.00"", that means that the last trade on that security, which the service is using to quote the security's price, was for 15500 shares at a price of $60 per share. Your guess is correct. The term ""institutional investor"" often is meant to include many types of institutions that would control large sums of money. This includes large banks, insurance companies, pooled retirement funds, hedge funds, and so on." Your assets are marked to market. If you buy at X, and the market is bidding at 99.9% * X then you've already lost 0.1%. This is a market value oriented way of looking at costs. You could always value your assets with mark to model, and maybe you do, but no one else will.  Just because you think the stock is worth 2*X doesn't mean the rest of the world agrees, evidenced by the bid.  You surely won't get any margin loans based upon mark to model.  Your bankers won't be convinced of the valuation of your assets based upon mark to model. By strictly a market value oriented way of valuing assets, there is a bid/ask cost. more clarification Relative to littleadv, this is actually a good exposition between the differences between cash and accrual accounting. littleadv is focusing completely on the cash cost of the asset at the time of transaction and saying that there is no bid/ask cost.  Through the lens of cash accounting, that is 100% correct. However, if one uses accrual accounting marking assets to market (as we all do with marketable assets like stocks, bonds, options, etc), there may be a bid/ask cost.  At the time of transaction, the bids used to trade (one's own) are exhausted.  According to exchange rules that are now practically uniform: the highest bid is given priority, and if two bids are bidding the exact same highest price then the oldest bid is given priority; therefore the oldest highest bid has been exhausted and removed at trade. At the time of transaction, the value of the asset cannot be one's own bid but the highest oldest bid leftover.  If that highest oldest bid is lower than the price paid (even with liquid stocks this is usually the case) then one has accrued a bid/ask cost.