Why is the difference between adjusted close and close price slightly different between each day?
Prices are adjusted for return and not payout.  So if you take the ratio of the close price and the adjusted close price, it should remain constant. The idea behind a total return (back-)adjustment is to give you a feeling how much money you would have needed back then to reach the price today under the premise that all distributions (dividends, spin-offs, etc.) are reinvested instantly and that reinvestment doesn't cost anything.
"The S&P 500 is an index. This refers to a specific collection of securities which is held in perfect proportion. The dollar value of an index is scaled arbitrarily and is based off of an arbitrary starting price. (Side note: this is why an index never has a ""split""). Lets look at what assumptions are included in the pricing of an index: All securities are held in perfect proportion. This means that if you invest $100 in the index you will receive 0.2746 shares of IBM, 0.000478 shares of General Motors, etc. Also, if a security is added/dropped from the list, you are immediately rebalancing the remaining money. Zero commissions are charged. When the index is calculated, they are using the current price (last trade) of the underlying securities, they are not actually purchasing them. Therefore it assumes that securities may be purchased without commission or other liquidity costs. Also closely related is the following. The current price has full liquidity. If the last quoted price is $20 for a security, the index assumes that you can purchase an arbitrary amount of the security at that price with a counterparty that is willing to trade. Dividends are distributed immediately. If you own 500 equities, and most distributed dividends quarterly, this means you will receive on average 4 dividends per day. Management is free. All equities can be purchased with zero research and administrative costs. There is no gains tax. Trading required by the assumptions above would change your holdings constantly and you are exempt from short-term or long-term capital gains taxes. Each one of these assumptions is, of course, invalid. And the fund which endeavors to track the index must make several decisions in how to closely track the index while avoiding the problems (costs) caused by the assumptions. These are shortcuts or ""approximations"". Each shortcut leads to performance which does not exactly match the index. Management fees. Fees are charged to the investor as load, annual fees and/or redemptions. Securities are purchased at real prices. If Facebook were removed from the S&P 500 overnight tonight, the fund would sell its shares at the price buyers are bidding the next market day at 09:30. This could be significantly different than the price today, which the index records. Securities are purchased in blocks. Rather than buying 0.000478 shares of General Motors each time someone invests a dollar, they wait for a few people and then buy a full share or a round lot. Securities are substituted. With lots of analysis, it may be determined that two stocks move in tandem. The fund may purchase two shares of General Motors rather than one of General Motors and Ford. This halves transaction costs. Debt is used. As part of substitution, equities may be replaced by options. Option pricing shows that ownership of options is equivalent to holding an amount of debt. Other forms of leverage may also be employed to achieve desired market exposure. See also: beta.  Dividends are bundled. VFINX, the largest S&P 500 tracking fund, pays dividends quarterly rather than immediately as earned. The dividend money which is not paid to you is either deployed to buy other securities or put into a sinking fund for payment. There are many reasons why you can't get the actual performance quoted in an index. And for other more exotic indices, like VIX the volatility index, even more so. The best you can do is work with someone that has a good reputation and measure their performance." For the case of spinoffs it reflects the market as activities as the specific steps that have to be followed take place. For example the spinoff of Leidos from SAIC in 2013. (I picked this one becasue I knew some of the details) On September 9, 2013, the Board of Directors of SAIC, Inc.(Ticker   Symbol (NYSE):SAI) approved the following:  The separation of its technical, engineering and enterprise information technology services business through the distribution of   shares of SAIC  Gemini, Inc. to stockholders.  Each stockholder of   record of SAIC, Inc. as of  September 19, 2013 (Record Date) will   receive one (1) share of SAIC Gemini, Inc. common stock for every   seven (7) shares of SAIC, Inc. common stock  held by such stockholder   as of the Record Date.   This distribution will be effective after   market close on September 27, 2013 (Distribution Date).  After the   Distribution Date, SAIC Gemini, Inc. will be renamed Science   Applications International Corporation (New SAIC). A one (1) for four (4) reverse stock split of the SAIC, Inc. common stock effective as of Distribution Date. After the Distribution Date,   SAIC, Inc. will be renamed Leidos Holdings, Inc. (Leidos). Q 11: What are the different trading markets that may occur between   Record Date and Distribution Date? A: Beginning two days prior to the Record Date of September 19, 2013   through the Distribution Date on September 27, 2013, there may be   three different trading markets available with respect to SAIC, Inc.   and the separation. Stock Ticker – SAI (Regular Way Trading with Due Bills): Shares of SAI common stock that trade on the regular-way market will trade with   an entitlement to shares of the New SAIC common stock distributed on   the Distribution Date.  Purchasers in this market are purchasing both   the shares of Leidos and New SAIC common stock. Form of Stock Ticker –SAIC (When Issued Trading): Shares of New SAIC common stock may be traded on a “when-issued” basis.  These   transactions are made conditionally because the security has been   authorized, but not yet issued.  Purchasers in this market are only   purchasing the shares of  New SAIC common stock distributed on the   Distribution Date. Form of Stock Ticker – LDOS (Ex-Distribution Trading): Shares that trade on the ex-distribution market will trade without an entitlement   to shares of New SAIC common stock distributed on the Distribution   Date.  Purchasers in this market are only purchasing the shares of   Leidos common stock. So the stock price for New SAIC starts a few days before the record date of 19 September 2013, while LDOS (new name for the old SAIC) goes back much earlier. But the company didn't split until after the close of business on 27 September 2013. http://investors.saic.com/sites/saic.investorhq.businesswire.com/files/doc_library/file/GeneralStockholder-QuestionsandAnswers.pdf diversifying; but isn't that what mutual funds already do? They diversify and reduce stock-specific risk by moving from individual stocks to many stocks, but you can diversify even further by selecting different fund types (e.g. large-cal, small-cap, fixed- income (bond) funds, international, etc.).  Your target-date fund probably includes a few different types already, and will automatically reallocate to less risky investments as you get close to the target date. I would look at the fees of different types of funds, and compare them to the historical returns of those funds.  You can also use things like morningstar and other ratings as guides, but they are generally very large buckets and may not be much help distinguishing between individual funds. So to answer the question, yes you can diversify further - and probably get better returns (and lower fees) that a target-date fund.  The question is - is it worth your time and effort to do so?  You're obviously comfortable investing for the long-term, so you might get some benefit by spending a little time looking for different funds to increase your diversification. Note that ETFs don't really diversify any differently than mutual funds, they are just a different mechanism to invest in funds, and allow different trading strategies (trading during the day, derivatives, selling short, etc.). A company's Return on Equity (ROE) is its net income divided by its shareholder's equity.  The shareholder's equity is the difference between total assets and total liabilities, and is not dependent on the stock price. What it takes to have a ROE over 100% is to have the income be greater than the equity.  This might happen for a variety of reasons, but one way a high ROE happens is if the shareholder's equity (the divisor) is small, which can occur if past losses have eroded the company's capital (the original invested cash and retained earnings).  If the equity has become a small value, the income for some period might exceed it, and so the ROE would be over 100%. Operating margin is not closely related to ROE.  Although operating income is related to net income, to calculate the margin you divide by sales, which is completely unrelated to shareholder's equity.  So there is no relationship with ROE to be expected.  Operating margin is primarily dependent on market conditions, and can be substantially different in different industries. "I'll answer this question: ""Why do intraday traders close their position at then end of day while most gains can be done overnight (buy just before the market close and sell just after it opens). Is this observation true for other companies or is it specific to apple ?"" Intraday traders often trade shares of a company using intraday leverage provided by their firm. For every $5000 dollars they actually have, they may be trading with $100,000, 20:1 leverage as an example. Since a stock can also decrease in value, substantially, while the markets are closed, intraday traders are not allowed to keep their highly leveraged positions opened. Probabilities fail in a random walk scenario, and only one failure can bankrupt you and the firm." Ya idk..I initially thought a moving average but that can't be it since when price crosses below trend line we see trend line continues to increase. https://villavu.com/forum/showthread.php?t=112371 but this says that it is in fact a monthly average. I don't see how that is possible, as adding a number below the average of a set to that set should decrease the average. People say 'the mean chases the margin,' not a fan of that terminology myself though.  Edit: ah wait the yellow line is daily average, not price. If monthly average is calculated on close price, then this is possible.  **so the answer then is the trend line is the monthly average**. You may simply be asking why stocks 'gap up' or 'gap down' when the stock market opens. This is because the price adjusts to news that occurred while the exchanges were closed overnight. Perhaps Asian stocks crashed, or perhaps a news story was released in the New York Times about some major company. There are thousands of factors that affect market sentiment, and the big gaps that happen at the open of every trading day is the price of the stocks catching up to those factors. "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."