In what ways is IEX different than a typical dark pool or a typical exchange?
You've said what's different in your question. There's 330 microseconds of network latency between IEX and anywhere else, so HFTs can't get information about trades in progress on IEX and use it to jump in ahead of those traders on other exchanges. All exchanges should have artificially induced latency of this kind so that if a trade is submitted simultaneously to all exchanges it reaches the furthest away one before a response can be received from the closest one, thus preventing HFT techniques.
If I buy VUSA from one exchange, can I sell it in a different exchange, assuming my brokerage account lets me trade in both exchanges? Or is it somehow tied to the exchange I bought it from? This doesn't happen for all securities and between all stock exchanges. So that is dependent on broker and country. I checked for VUSA with Selftrade. They categorically refused allowing me to trade in VUSA in different exchanges. I can only buy and sell in same currency only, albeit sell(buy) in the same exchange where I buy(sell) from. Should be the same behaviour for all brokers for us mere mortals, if you are a bank or a millionaire than that might be a different question.  The VUSA you quote is quoted in GBP in LSE and in EUR in AEX, and the ETF has been created by an Irish entity and has an Irish ISIN.  As Chris mentioned below, happens between US and Canadian exchanges, but not sure it happens across all exchanges. You cannot deal in inter-listed stocks in LSE and NYSE. Since it's the same asset, its value should not vary across exchanges once you compensate for exchange rates, right? Yes, else it opens up itself for arbitrage (profit without any risk) which everybody wants. So even if any such instance occurs, either people will exploit it to make the arbitrage profit zero (security reflects the equilibrium price) or the profit from such transaction is so less, compared with the effort involved, that people will tend to ignore it. Anyways arbitrage profit is very difficult to garner nowadays, considering the super computers at work in the market who exploit these discrepancies, the moment they see them and bring the security right to the zero arbitrage profit point. If there's no currency risk because of #2, what other factors should I consider when choosing an exchange to trade in? Liquidity? Something else? Time difference, by the time you wake up to trade in Japan, the Japanese markets would have closed. Tax implications across multiple continents. Law of the land, providing protection to investors. Finding a broker dealing in markets you want to explore or dealing with multiple brokers. Regulatory headaches. Option tiers are broker specific, according mostly to their business model and presumably within the bounds of FINRA Rule 2111 (Suitability). The tier system can be as complex as E*Trade or as simple as none with Interactive Brokers. The suitability is determined presumably by compliance presumably by the legal history of the rule. The exact reasoning is political, effected by the relevant party composition of the legislature and executive. The full legal history will have the judiciary's interpretations of legislation and policy. Cash and margin rules are dictated primarily by the Federal Reserve and more precisely by FINRA and the SEC.  This is the only distinction made by IB. As Chris pointed out in his comment, smaller stock exchanges may use open outcry. There are several exchanges that use open outcry/floor trading in the US, however, although they aren't necessarily stock exchanges.  Having visited the three Chicago exchanges I mentioned, I can personally vouch for their continued use of a trading floor, although its use is declining in all three. "Pay to play? You mean they pay for beefier data feeds that other firms don't need, sure they do. But everyone can trade on the US exchanges now (NYSE, NASDAQ, BATS, etc) which was not true 20 years ago when NYSE had the specialist monopoly, so yes the markets are more democratic than they've ever been.  Side note, the exchanges do directly profit from increased trading volume because they take a small % of every trade, so I'm not sure what you mean they don't directly profit from it.  Also I get the feeling you don't understand the scope of HFT activity, HFT peak profits were on the order of 7 billion during the highest volume time of the last decade (2005-2010). They are now around 1B. Compared to the trillions of dollars that change hands in the exchange per year, this is chump change, hardly a ""free money faucet"".  Also Katsayuma opened yet another dark pool that caters to high volume clients (your goldmans and merrils). The only difference in IEX is it got a free marketing campaign to entice clients. Seriously, IEX is nothing more than the existing fixed cross dark pools, which btw screws over retail investors more than the lit exchanges like NASDAQ.   Katsayuma got steamrolled in his executions because he couldn't keep up with the time and then hit the lottery jackpot by getting Michael Lewis to paint him as a ""hero"", honestly I'm confounded at how lucky that dude got.  BTW broker dealers get preferential treatment in IEX, meaning they get to cut in front of the line in front of retail investors. Why are you so opinionated about this, did you make a few bad trades on eTrade and need a scapegoat?" The NYSE is not the only exchange in the world (or even the only one in the USA). Amazingly, the London stock exchange works on London time, the Shanghai exchange works on Shanghai time and the Australian stock exchange works on Sydney time. In addition futures exchanges work overnight. You can trade currency ETF options on IB. It is SIPC insured; the options are just like vanilla options in Saxo. IESC has a one-time, non-repeatable event in its operating income stream.  It magnifies operating income by about a factor of five.  It impacts both the numerator and the denominator.  Without knowing exactly how the adjustments are made it would take too much work for me to calculate it exactly, but I did get close to their number using a relatively crude adjustment rule. Basically, Yahoo is excluding one-time events from its definitions since, although they are classified as operating events, they distort the financial record.  I teach securities analysis and have done it as a profession.  If I had to choose between Yahoo and Marketwatch, at least for this security, I would clearly choose Yahoo. Like Ganesh, I've used XE Trade - however I still do, fairly often.  I have never had a single problem with them regardless of the method I used to move money -- Draft, Wire, ACH, bill payment through online banking, etc. The type of trade I do most often is online bill payment to ACH -- i.e. I pay through my banking site and they pay through ACH.  There's no fee and it takes 2 business days to go through.  I do mainly CAD to USD conversions and I lose about 1.25 cents on the rate -- for example, if the CAD is worth 95 cents US, converting $100 CAD would get me $92.75 USD.  The banks usually take 2.5% or so, so it's 50% savings. It was free and pretty simple to sign up, all online -- and besides the standard info all they required was for me to upload a scan of a bank statement. As for an API, I have no idea if they have one. I'm not disputing whether IB is good to start. I'm disputing that anything going through them is 'low latency.' 50-100ms is a lifetime against high frequency traders. Also, if you're co-locating w/ them and using a direct feed and still getting that latency you're getting ripped off. It should take 100ms *for a message to travel between Chicago and NY*, let alone between your computer and the exchange one at the same colo. "Exchange A has 100 shares of a stock at $10, the next 100 shares cost $10.01. Exchange B has the same pricing structure.  A fund manager wants to buy 200 shares of the stock, and decides that buying 100 shares at $10 from each exchange will be cheaper than staying in one exchange and paying $10.01 for the second half of his order.  The manager places two separate orders. Let's say the first order reaches exchange A, and the trade executes at $10. Traders (algorithms) on exchange B see this happen, and adjust their price up to $10.01 accordingly. Now, when the manager's order reaches exchange B, there will no longer be any shares trading at $10.  Some people say that this is front running, but if the manager only wanted 100 shares, the price would have still shifted. Some say this creates a more efficient market with tighter spreads due to the decreased risk to the market maker, but it also means the aggregate bid-ask offers across multiple exchanges are not necessarily accurate, creating a ""false liquidity"". You can decide for yourself whether or not this is a good thing." "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." Different exchanges sometimes offer different order types, and of course have different trading fees.  But once a trade is finished, it should not matter where it was executed. He said he's using MSCI World as a benchmark. MSCI World is not an exchange. The point is the same security listed in different places has different prices, so how do you describe the equity beta of the company to MSCI World if you have multiple and different return streams? This is a real problem to consider and you just dismiss it entirely. Liquidity on dual listed equities is rarely the same on both exchanges. More liquidity means you would typically get a better price assuming you execute the trades using the same order types. It's recommended to trade where the liquidity is greater unless your trading method benefits somehow from it being lower. It's important to remember that some ADRs (some European companies listed in US) have ADR fees which vary. USD/EUR transaction fees are low when using a decent broker but you're obviously participating in the currency risk. "In the first situation you describe, any intelligent routing algo will send a 1000 lot order to the lit exchange in step 1. Then you get filled 1000@$10. After the fill occurs, the matching engine tells everyone what happened.   If the order book consists of 100 orders of 1 lot @ $10, and you place a ""buy 100 lots"" order, here is what happens:  1. The matching engine receives your order. 2. The matching engine matches your order against the 100 individual orders on the book. 3. The matching engine broadcasts 100 trade notifications.   No one has any opportunity to cancel their orders since they only hear of the fill after it happened.   The only way someone would have the opportunity to cancel is if there was 500 lots on one exchange and 500 on another. Then someone might observe a trade on exchange #1 and cancel their sell order on exchange #2 in response."