Trading when you work for a market participant
Ask someone in Human Resources. I seriously doubt you are the first person to ask this question for their company and they should be more than happy to help. There is normally a policy at the organisation that would restrict trades or allow trades under certain conditions. This would be in accordance with the current regulations as well as Institutions own ethical standards.  Typical I have seen is that Technology roles are to extent not considered sensitive, ie the employees in this job function normally do not access sensitive data [unless your role is analyst or production support]. An employee in exempt roles are allowed to trade in securities directly with other broker or invest in broad based Mutual Funds or engage a portfolio management services from a reputed organisation. It is irrelevant that your company only deals with amounts > 1 Million, infact if you were to know what stock the one million is going into, you may buy it slightly earlier and when the company places the large order, the stock  typically moves upwards slightly, enough for you to make some good money. That is Not allowed. But its best you get hold of a document that would layout the do' and don't in your organisation. All such organisation are mandated to have a written policy in this regard.
"NASDAQ has Pre and After market : NASDAQ Trading Schedule Regular Trading Session Schedule The NASDAQ   Stock Market Trading Sessions (Eastern Time) Pre-Market Trading Hours from 4:00 a.m. to 9:30 a.m.   Market Hours from 9:30 a.m. to 4:00 p.m.   After-Market Hours from 4:00 p.m. to 8:00 p.m.   Quote and order-entry from 4:00 a.m. to 8:00 p.m.   Quotes are open and firm from 4:00 a.m. to 8:00 p.m. You can trade in Pre/After Market but liquidity is very low. If an ""unexpected world events"" occurs, the volume/liquidity will most certainly increase. Another example is the Forex Market that's open 24/7 around the world. As one major forex market closes, another one opens. According to GMT,   for instance, forex trading hours move around the world like this:   available in New York between 01:00 pm – 10:00 pm GMT; at 10:00 pm GMT   Sydney comes online; Tokyo opens at 00:00 am and closes at 9:00 am   GMT; and to complete the loop, London opens at 8:00 am and closes at   05:00 pm GMT. This enables traders and brokers worldwide, together   with the participation of the central banks from all continents, to   trade online 24 hours a day. src" It depends on the market that you participate in. Stock markets are not zero sum as JoeTaxpayer explained. On the other hand, any kind of derivative markets (such as options or futures) are indeed zero sum, due to the nature of the financial instruments that are exchanged. Those markets tend to be more unforgiving. I don't have evidence for this, but I believe one of the reasons that investors so often lose their money is psychology. The majority of us as humans are not wired to naturally make the kinds of rigorous and quick decisions that markets require, especially if day trading. Some people can invest time and energy to improve themselves and get over that. Those are the ones who succeed. "Traders = every market participant. Not some shadow figure that excludes you just because you passively drop cash into a 401k Vanguard fund every paycheck. So yes, if everyone stopped trading then the price won't move. Trades are 100% responsible for the prices you see on charts and tickers. A stock won't be worth ""$100"" if nobody ever traded $100 for it. It only has that price now or in the past because somebody placed an order for it at $100 and somebody else filled that order at $100" "Say we have stock XYZ that costs $50 this second. It doesn't cost XYZ this second. The market price only reflects the last price at which the security traded. It doesn't mean that if you'll get that price when you place an order. The price you get if/when your order is filled is determined by the bid/ask spreads. Why would people sell below the current price, and not within the range of the bid/ask? Someone may be willing to sell at an ask price of $47 simply because that's the best price they think they can sell the security for. Keep in mind that the ""someone"" may be a computer that determined that $47 is a reasonable ask price. Remember that bid/ask spreads aren't fixed, and there can be multiple bid/ask prices in a market at any given time. Your buy order was filled because at the time, someone else in the market was willing to sell you the security for the same price as your bid price. Your respective buy/sell orders were matched based on their price (and volume, conditional orders, etc). These questions may be helpful to you as well: Can someone explain a stock's ""bid"" vs. ""ask"" price relative to ""current"" price? Bids and asks in case of market order Can a trade happen ""in between"" the bid and ask price? Also, you say you're a day trader. If that's so, I strongly recommend getting a better grasp on the basics of market mechanics before committing any more capital. Trading without understanding how markets work at the most fundamental levels is a recipe for disaster." The best way to make money during a market correction is to be a financial services company handling transactions for people who think they can beat the market, and charging a percentage commission on each transaction, while keeping your own money somewhere nice and safe, stable and low-fee. "Other than the brokerage fee you should also consider the following: Some brokerages provide extra protection against the these and as you guessed it for a fee. However, there could be a small bonus associated with your trading at scale: You are probably qualified for rebates from the exchanges for generating liquidity.  ""Fees and Credits applicable to Designated Market Makers (“DMMs”)"" https://www.nyse.com/publicdocs/nyse/markets/nyse/NYSE_Price_List.pdf All in all, I will say that it will be really hard for you to avoid paying brokerage fee and yes, even Buffet pays it." ETFs are legally required to publicly disclose their positions at every point in time. The reason for this is that for an ETF to issue shares of ETF they do NOT take cash in exchange but underlying securities - this is called a creation unit. So people need to know which shares to deliver to the fund to get a share of ETF in exchange. This is never done by retail clients, however, but by nominated market makers. Retail persons will normally trade shares only in the secondary market (ie. on a stock exchange), which does not require new shares of the ETF to be issued. However, they do not normally make it easy to find this information in a digestible way, and each ETF does it their own way. So typically services that offer this information are payable (as somebody has to scrape the information from a variety of sources or incentivise ETF providers to send it to them). If you have access to a Bloomberg terminal, this information is available from there. Otherwise there are paid for services that offer it. Searching on Google for ETF constituent data, I found two companies that offer it: See if you can find what you need there. Good luck. (etfdb even has a stock exposure tool freely available that allows you to see which ETFs have large exposure to a stock of your choosing, see here: http://etfdb.com/tool/etf-stock-exposure-tool/). Since this data is in a table format you could easily download it automatically using table parsing tools for your chosen programming language. PS: Don't bother with underlying index constituents, they are NOT required to be made public and index providers will normally charge handsomely for this so normally only institutional investors will have this information. "Trading on specific ECNs is the easy part - you simply specify the order routing in advance.  You are not buying or selling the *exact* same shares.  Shares are fungible - so if I simultaneously buy one share and sell another share, my net share position is zero - even if those trades don't settle until T+3.  PS ""The Nasdaq"" isn't really an exchange in the way that the CME, or other order-driven markets are.  It's really just a venue to bring market makers together.  It's almost like ""the internet,"" as in, when you buy something from Amazon, you're not buying it from ""the internet,"" but it was the internet that made your transaction with Amazon possible."