Why Google Finance puts to two decimal places for the trading volumes?
Many brokerages offer automatic dividend reinvestment. It is very infrequent that these dividends are exactly a whole share. So, if you have signed up for automatic dividend reinvestment, many brokerages will reinvest your dividends and assign to you a fractional share. I can't speak for how these shares work with regards to voting, but I can say that the value of these fractional holdings does change with stock price as if one genuinely could hold a fraction of a share.
"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." In the scenario you describe, the first thing I would look at would be liquidity.  In other words, how easy is it to buy and sell shares.  If the average daily volume of one share is low compared to the average daily volume of the other, then the more actively traded share would be the more attractive.  Low volume shares will have larger bid-offer spreads than high volume shares, so if you need to get out of position quickly you will be at risk of being forced to take a lowball offer. Having said that, it is important to understand that high yielding shares have high yields for a reason.  Namely, the market does not think much of the company's prospects and that it is likely that a cut in the dividend is coming in the near future. In general, the nominal price of a share is not important.  If two companies have equal prospect, then the percentage movement in their share price will be about the same, so the net profit or loss you realise will be about the same. "You can infer some of the answers to your questions from the BATS exchange's market data page and its associated help page.  (I'm pretty sure a page like this exists on each stock exchange's website; BATS just happens to be the one I'm used to looking at.) The Matched Volume section refers to all trades on a given date that took place on ""lit"" exchanges; that is, where a public protected US stock exchange's matching engine helped a buyer and a seller find each other.  Because there are exactly 11 such exchanges in existence, it's easy to show 100% of the matched volume broken down into 11 rows. The FINRA & TRF Volume section refers to all trades on a given date that took place on ""non-lit"" exchanges.  These types of trades include dark pool volume and any other trade that is not required to take place in public but is required to be reported (the R in TRF) to FINRA.  There are three venues via which these trades may be reported to FINRA -- NASDAQ's, NYSE's, and FINRA's own ADF.  They're all operated under the purview of FINRA, so the fact that they're ""located at"" NASDAQ or NYSE is a red herring.  (For example, from the volume data it's clear that the NASDAQ facility does not only handle NASDAQ-listed (Tape C) securities, nor does the NYSE facility only handle NYSE-listed (Tape A) securities or anything like that.) The number of institutions reporting to each of the TRFs is large -- many more than the 11 public exchanges -- so the TRF data is not broken down further.  (Also I think the whole point of the TRFs is to report in secret.)  I don't know enough details to say why the NASDTRF has always handled more reporting volume than the other two facilities.  Of course, since we can't see inside the TRF reporting anyway, it's sort of a moot point." Volume @ 0 doesn't mean that there are no buyers and sellers, it just means that there hasn't been any trades done yet. What you need to look for are the bids and offers (for selling and buying, respectively). For further expiration and NTM or IT options there will almost always be a bid and an offer (but it may be very wide). Now, in case where there is 0 bid (no one is willing to buy), you may still have a chance if the option has some value in it. For that - you need your broker to try to shop it to market making firms. Now, depending on who your broker is, this may or may not be possible. Alternatively, if you have DMA (direct market access) to the options exchanges, you can try to put in an offer of your own and wait for someone to execute against you, however do not expect to be traded with unless your price is out of line with the cost. However, in wide markets, you can try Lampost options (they may give you price improvement) or try to offer very close to the bid. You may save yourself a penny or two and perhaps get a rebate if you are using BATSO or NASDAQO markets (if you have DMA and pass-through exchange fees). Because someone smarter than you by 50 IQ points (a quant) will depart their larger position long before you have a chance to see it coming. Your stop losses are useless as the market will open with the issue below your sell price. Your trade even if place at the same mine would settle after theirs. don't piss in the tall grass with the big dogs. If they are wrong or right does not matter you will be haircut or whipsawed. I stumbled on the same discrepancy, and was puzzled by a significant difference between the two prices on ETR and FRA. For example, today is Sunday, and google shows the following closing prices for DAI. FRA:DAI: ETR:DAI: So it looks like there are indeed two different exchanges trading at different prices.  Now, the important value here, is the last column (Volume). According to Wikipedia, the trading on Frankfort Stock Exchange is done today exclusively via Xetra platform, thus the volume on ETR:DAI is much more important than on FRA:DAI.  Obviously, they Wikipedia is not 100% accurate, i.e. not all trading is done electronically via Xetra. According to their web-page, Frankfort exchange has a Specialist Trading on Frankfurt Floor service which has slightly different trading hours.  I suspect what Google and Yahoo show as Frankfort exchange is this manual trading via a Specialist (opposed to Xetra electronic trading). To answer your question, the stock you're having is exactly the same, meaning if you bought an ETR:BMW you can still sell it on FRA (by calling a FRA Trading Floor Specialist which will probably cost you a fee). On the other hand, for the portfolio valuation and performance assessments you should only use ETR:BMW prices, because it is way more liquid, and thus better reflect the current market valuation. "You gotta stop using that ""overhears"" argument. It's ridiculous. First of all it doesn't work like that because most trades get filled internally or through dark pools and secondly the HFT is taking risk for that 2 cents. Also, they don't hold it, they gotta offload it, so the price will go back down. Finally, this only affects people making huge orders and this is pennies to them. This is not a free lunch for HFT since those 2 cents have risks associated.  Think of it another way: some HFT dudes have some programs that run really fast, and they make some minuscule amounts of money; think maybe a few k a day. But, they do do something useful: they let you enter/exit positions at a better price by reducing spreads." I think George's answer explains fairly well why the brokerages don't allow this - it's not an exchange rule, it's just that the brokerage has to have the shares to lend, and normally those shares come from people's margin, which is impossible on a non-marginable stock. To address the question of what the alternatives are, on popular stocks like SIRI, a deep In-The-Money put is a fairly accurate emulation of an actual short interest.  If you look at the options on SIRI you will see that a $3 (or higher) put has a delta of -$1, which is the same delta as an actual short share. You also don't have to worry about problems like margin calls when buying options.  The only thing you have to worry about is the expiration date, which isn't generally a major issue if you're buying in-the-money options... unless you're very wrong about the direction of the stock, in which case you could lose everything, but that's always a risk with penny stocks no matter how you trade them. At least with a put option, the maximum amount you can lose is whatever you spent on the contract.  With a short sale, a bull rush on the stock could potentially wipe out your entire margin.  That's why, when betting on downward motion in a microcap or penny stock, I actually prefer to use options.  Just be aware that option contracts can generally only move in increments of $0.05, and that your brokerage will probably impose a bid-ask spread of up to $0.10, so the share price has to move down at least 10 cents (or 10% on a roughly $1 stock like SIRI) for you to just break even; definitely don't attempt to use this as a day-trading tool and go for longer expirations if you can.