If NYSE has market makers, what is the role of NYSE ARCA which is an ECN
Electronic trading is many orders of magnitude cheaper and more liquid than floor trading and is rapidly displacing it. Stil, electronic trading accounts for 79% of stock trading volume in the U.S. Polcari is losing the battle. Floor trading is still offered, but it's only used for bulk orders, so electronic trading is servicing small trades at minimum prices while floor trading is now the concierge service. I would say it's a bit more complicated than that. Do you understand what a market maker does?  An ECN (electronic communication network) is a virtual exchange that works with market makers. Using a rebate structure that works by paying for orders adding liquidity and charges a fee for removing liquidity. So liquidity is created by encouraging what are essentially limit orders, orders that are outside of the current market price and therefore not immediately executable. These orders stay in the book and are filled when the price of the security moves and triggers them.  So direct answer is NYSE ARCA is where market makers do their jobs. These market makers can be floor traders or algorithmic. When you send an order through your brokerage, your broker has a number of options. Your order can be sent directly to an ECN/exchange like NYSE ARCA, sent to a market making firm like KCG Americas (formerly Knight Capital), or internalized. Internalization is when the broker uses an in house service to execute your trade. Brokerages must disclose what they do with orders. For example etrade's. https://content.etrade.com/etrade/powerpage/pdf/OrderRouting11AC6.pdf This is a good graphic showing what happens in general along with the names of some common liquidity providers. http://www.businessweek.com/articles/2012-12-20/how-your-buy-order-gets-filled
You seem to think that stock exchanges are much more than they actually are. But it's right there in the name: stock exchange. It's a place where people exchange (i.e. trade) stocks, no more and no less. All it does is enable the trading (and thereby price finding). Supposedly they went into mysterious bankruptcy then what will happen to the listed companies  Absolutely nothing. They may have to use a different exchange if they're planning an IPO or stock buyback, that's all. and to the shareholder's stock who invested in companies that were listed in these markets ?  Absolutley nothing. It still belongs to them. Trades that were in progress at the moment the exchange went down might be problematic, but usually the shutdown would happen in a manner that takes care of it, and ultimately the trade either went through or it didn't (and you still have the money). It might take some time to establish this. Let's suppose I am an investor and I bought stocks from a listed company in NYSE and NYSE went into bankruptcy, even though NYSE is a unique business, meaning it doesn't have to do anything with that firm which I invested in. How would I know the stock price of that firm  Look at a different stock exchange. There are dozens even within the USA, hundreds internationally. and will I lose my purchased stocks ?  Of course not, they will still be listed as yours at your broker. In general, what will happen after that ?  People will use different stock exchanges, and some of them migth get overloaded from the additional volume. Expect some inconveniences but no huge problems. I was looking at NAT and NAO, NAT owns 20% of NAO.  They trade opposite each other on the price of oil, low is good for NAT, bad for NAO.  In bad times the other company's stock would probably rise, so they could trim excess shares to keep a stable monetary holding.  This would create cash in bad times, in good times they could buy more, creating a floor as well for the other. If the share is listed on a stock exchange that creates liquidity and orderly sales with specialist market makers, such as the NYSE, there will always be a counterparty to trade with, though they will let the price rise or fall to meet other open interest.  On other exchanges, or in closely held or private equity scenarios, this is not necessarily the case (NASDAQ has market maker firms that maintain the bid-ask spread and can do the same thing with their own inventory as the specialists, but are not required to by the brokerage rules as the NYSE brokers are).  The NYSE has listing requirements of at least 1.1 million shares, so there will not be a case with only 100 shares on this exchange. I used to be a trader at a desk that sold delta-one derivatives on listed indices (think swaps, ETFs). There is a LOT to do:   buy/ sell stocks according to redemptions or new orders; manage the currency exposure; indices rebalance their composition everyday based on stock corporate actions, dividends and index reviews - you need to be aware of each and everyone and rebalance your portfolio to account for it; manage your inventory to get the best repo rates possible; trade single stock swaps with foreign counterparties to get access to better tax rates on dividends; when you have a big order where certain stock orders may not get filled - you have to create a strategy for managing that risk; sometimes you hedge your positions using futures that expire every three months in which case you need to figure out the best times to roll your expiring futures; i could go on and on.  Basically, since the profit margins are so low, the market so competitive for such vanilla products, and the volumes so high, you have to really make your processes super efficient and error-proof. Trust me, there is a lot to be done! "There are people (well, companies) who make money doing roughly what you describe, but not exactly. They're called ""market makers"". Their value for X% is somewhere on the scale of 1% (that is to say: a scale at which almost everything is ""volatile""), but they use leverage, shorting and hedging to complicate things to the point where it's nothing like a simple as making a 1% profit every time they trade. Their actions tend to reduce volatility and increase liquidity. The reason you can't do this is that you don't have enough capital to do what market makers do, and you don't receive any advantages that the exchange might offer to official market makers in return for them contracting to always make both buy bids and sell offers (at different prices, hence the ""bid-offer spread""). They have to be able to cover large short-term losses on individual stocks, but when the stock doesn't move too much they do make profits from the spread. The reason you can't just buy a lot of volatile stocks ""assuming I don't make too many poor choices"", is that the reason the stocks are volatile is that nobody knows which ones are the good choices and which ones are the poor choices. So if you buy volatile stocks then you will buy a bunch of losers, so what's your strategy for ensuring there aren't ""too many""? Supposing that you're going to hold 10 stocks, with 10% of your money in each, what do you do the first time all 10 of them fall the day after you bought them? Or maybe not all 10, but suppose 75% of your holdings give no impression that they're going to hit your target any time soon. Do you just sit tight and stop trading until one of them hits your X% target (in which case you start to look a little bit more like a long-term investor after all), or are you tempted to change your strategy as the months and years roll by? If you will eventually sell things at a loss to make cash available for new trades, then you cannot assess your strategy ""as if"" you always make an X% gain, since that isn't true. If you don't ever sell at a loss, then you'll inevitably sometimes have no cash to trade with through picking losers. The big practical question then is when that state of affairs persists, for how long, and whether it's in force when you want to spend the money on something other than investing. So sure, if you used a short-term time machine to know in advance which volatile stocks are the good ones today, then it would be more profitable to day-trade those than it would be to invest for the long term. Investing on the assumption that you'll only pick short-term winners is basically the same as assuming you have that time machine ;-) There are various strategies for analysing the market and trying to find ways to more modestly do what market makers do, which is to take profit from the inherent volatility of the market. The simple strategy you describe isn't complete and cannot be assessed since you don't say how to decide what to buy, but the selling strategy ""sell as soon as I've made X% but not otherwise"" can certainly be improved. If you're keen you can test a give strategy for yourself using historical share price data (or current share price data: run an imaginary account and see how you're doing in 12 months). When using historical data you have to be realistic about how you'd choose what stocks to buy each day, or else you're just cheating at solitaire. When using current data you have to beware that there might not be a major market slump in the next 12 months, in which case you won't know how your strategy performs under conditions that it inevitably will meet eventually if you run it for real. You also have to be sure in either case to factor in the transaction costs you'd be paying, and the fact that you're buying at the offer price and selling at the bid price, you can't trade at the headline mid-market price. Finally, you have to consider that to do pure technical analysis as an individual, you are in effect competing against a bank that's camped on top of the exchange to get fastest possible access to trade, it has a supercomputer and a team of whizz-kids, and it's trying to find and extract the same opportunities you are. This is not to say the plucky underdog can't do well, but there are systematic reasons not to just assume you will. So folks investing for their retirement generally prefer a low-risk strategy that plays the averages and settles for taking long-term trends." The process would look something like:  1. Register your investment company with the SEC 2. Get the ETF approved by the SEC  3. Get a custodian bank (likely requires min assets of a few million) 4. Get listed on an exchange like NYSEARCA by meeting requirements and have an IPO   1 and 2 probably require a lot of time and fees and would be wise to have a lawyer advising, 3 is obviously difficult due to asset requirements and 4 would probably involve an investment bank plus more fees "In the US, stocks are listed on one exchange but can be traded on multiple venues.  You need to confirm exactly what your data is showing: a) trades on the primary-listed exchange; or b) trades made at any venue. Also, the trade condition codes are important.  Only certain trade condition codes contribute towards the day's open/high/low/close and some others only contribute towards the volume data.  The Consolidated Tape Association is very clear on which trades should contribute towards each value - but some vendors have their own interpretation (or just simply an erroneous interpretation of the specifications). It may surprise you to find that the majority of trading volume for many stocks is not on their primary-listed exchange.  For example, on 2 Mar 2015, NASDAQ:AAPL traded a total volume across all venues was 48096663 shares but trading on NASDAQ itself was 12050277 shares. Trades can be cancelled.  Some data vendors do not modify their data to reflect these busted trades.   Some data vendors also ""snapshot"" their feed at a particular point in time of the data.  Some exchanges can provide data (mainly corrections) 4-5 hours after the closing bell.  By snapshotting the data too early and throwing away any subsequent data is a typical cause of data discrepancies.   Some data vendors also round prices/volumes - but stocks don't just trade to two decimal places. So you may well be comparing two different sets of trades (with their own specific inclusion rules) against the same stock.  You need to confirm with your data sources exactly how they do things. Disclosure: Premium Data is an end-of-day daily data vendor." Since I've been doing this since late 03 I have colo machines in Chicago and NYC, and have direct exchange data feeds etc.  I mentioned in a prior post though, for someone starting out on algorithmic trading, I'd recommend Nanex for tick data and Interactive Brokers for your brokerage account. IB has a robust and easy to use API. It won't let you do the most low latency stuff bc you can't colo at the exchange and have to clear through their order management systems but if you are looking at opportunities that exist in the market in excess of 50ms it's probably a good place to start. If not, go Lightspeed imo, but that'll cost you on the colo/data a lot more. Whilst it is true that they do not have a conference call every time a rating is produced, the parameters of a natural oligopoly do indicate that there are negative effects of deviating too much from the other members of an oligopoly.   There are instances of rating agencies (Moody's) giving lower ratings to punish the issuer for going elsewhere (Re Hannover), but usually a slightly lower rating may be acceptable and is usually corrected to be in line with the competitor shortly afterwards. The power, arguably, is with the issuer in this sense because they can take their business to the 3rd member (Fitch) if the rating is too low from one of the Big Two. The preservation of the 'Big Two', for so long, is arguably testament to the S&amp;P and Moody's understanding of these parameters  If the answer is not micromanaging, what do you think it is out of interest? "I'm not sure which article you are referring to- if you are talking about the convergex article.... it literally describes what they did in the article.   Tradeworx and software company thesys(both founded by manoj narang) provide data to the sec and function as market makes- they are highly respected and handle over 5% of us equity by volume.   Their ""head people"" is manoj narang. I don't think he ""bailed out"". As you can read [here](https://research-doc.credit-suisse.com/docView?sourceid=em&amp;document_id=x569866&amp;serialid=lZPbU6l0cgAqB%2B1gg4uZFLk14dBwhfSb9lZ3%2BdmPHV4%3D) they are willing 53% of the trades they place everyday and have   He has stated in an interview he wants to explore options trading.   They were debunking myths because of the regulators wanted answers and at the time hft was not understood very well. Narang also testified at a senate committee[video here](https://youtu.be/NG47K41Q7KA)" "Generally, ETFs work on the basis that there exists a pair of values that can be taken at any moment in time: A Net Asset Value of each share in the fund and a trading market price of each share in the fund.  It may help to picture these in baskets of about 50,000 shares for the creation/redemption process. If the NAV is greater than the market price, then arbitrageurs will buy up shares at the market price and do an ""in-kind"" transaction that will be worth the NAV value that the arbitrageurs could turn around and sell for an immediate profit. If the market price is greater than the NAV, then the arbitrageurs will buy up the underlying securities that can be exchanged ""in-kind"" for shares in the fund that can then be sold on the market for an immediate profit. What is the ETF Creation/Redemption Mechanism? would be a source on this though I imagine there are others. Now, in the case of VXX, there is something to be said for how much trading is being done and what impact this can have. From a July 8, 2013 Yahoo Finance article: At big option trade in the iPath S&P 500 VIX Short-Term Futures Note   is looking for another jump in volatility.  More than 250,000 VXX options have already traded, twice its daily   average over the last month. optionMONSTER systems show that a trader   bought 13,298 August 26 calls for the ask price of $0.24 in volume   that was 6 times the strike's previous open interest, clearly   indicating new activity. Now the total returns of the ETF are a combination of changes in share price plus what happens with the distributions which could be held as cash or reinvested to purchase more shares." "Not arguing w that at all, and you can't colo w IB afaik. Their API over WAN, VPN or CTCI on direct line only. If you colo at Nasdaq and clear through Lightspeed you're talking microseconds (which is where my actual low latency strats are). But yes, I suppose for IB I should have mentioned ""low-ish"" latency rather than actual low latency. So I'll add a caveat to the newbs - don't try to do ECN arb (or any other super-low-latency strat) or market-make (their cancel fees will kill you) the entire equity universe through IB. It won't work. They're not suitable for that.  My 50-100 reference was for WAN IB clearing for these guys probably using their API through IB gateway or TWS, which is how most would likely start. Doubt they're diving head first into ECN arb day one - they probably wouldn't be doing lowest latency stuff, most peeps start w some sort of trend following strat in my exp and you can work on those timescales w those. Trying to give advice for people starting out, not for other already pro algo traders.  But yes, finprogger is correct, IB would not be a suitable broker to use for a competitive ultra low-latency strat. They are too slow." Which is what [flash trading](http://www.investopedia.com/financial-edge/0809/flash-trading-wall-streets-latest-scam.aspx) is for.   edit: I promise you, you could. You would just need a faster line. I promise that's why the NYSE banned it. However, that still doesn't mitigate the problem of creating your own exchange. I'm not in the business but I've always thought that Catalyst + industry context = market beating returns.  Meaning that if you know what an event means faster than everyone else you can make money.  Though I don't know how you'd express that in a report.  An example that comes to mind is when Japan announced they were forming a consortium, the largest in the world, to make LCD panel glass.  After that I got the heck of GLW though the stock price kept going up at the time.  It is like no one understood the implications. No, it's not even remotely accurate in the current sense. Both markets have counterparties directly executing against one another, and both have auctions. The auction mechanics are different (with NYSE's Specialist/DMM model) but during normal market hours there isn't much difference.