How does historical data get adjusted for dividends, exactly?
Various types of corporate actions will precipitate a price adjustment.  In the case of dividends, the cash that will be paid out as a dividend to share holders forms part of a company's equity.  Once the company pays a dividend, that cash is no longer part of the company's equity and the share price is adjusted accordingly. For example, if Apple is trading at $101 per share at the close of business on the day prior to going ex-dividend, and a dividend of $1 per share has been declared, then the closing price will be adjusted by $1 to give a closing quote of $100. Although the dividend is not paid out until the dividend pay date, the share price is adjusted at the close of business on the day prior to the ex-dividend date since any new purchases on or after the ex-dividend date are not entitled to receive the dividend distribution, so in effect new purchases are buying on the basis of a reduced equity.   It will be the exchange providing the quote that performs the price adjustment, not Google or Yahoo.  The exchange will perform the adjustment at the close prior to each ex-dividend date, so when you are looking at historical data you are looking at price data that includes each adjustment. If you download the historical data from Yahoo, you will see two different close prices. The one labeled 'Close' is simply the price that was quoted on that particular day. The one labeled 'Adj Close' is the close price that has been adjusted for any splits and dividends that have occurred after that date.  For example, if a stock splits 10:1 on a particular date, then the adjusted close for all dates prior to that split will have been divided by 10. If a dividend is paid, then all dates prior will have that amount subtracted from their adjusted quote. Using the adjusted close allows you to compare any two dates and see the true relative return. According to Active Equity Management by Zhou and Jain: When a stock pays dividend, the adjusted price in Yahoo makes the following adjustment: Let T be the ex-dividend date (the first date that the buyers of a stock will not receive the dividend) and T-1 be the last trading day before T. All prices before T are adjusted by a multiplier (C_{T-1} - d_T)/C_{T-1}, where C_{T-1} is the close price at T-1 and d_T is the dividend per share. This, of course means that the price before T decreases. "I had  both closing price and adjusted price of Apple showing the same amount after ""download data"" csv file was opened in excel. https://finance.yahoo.com/quote/AAPL/history?period1=1463599361&period2=1495135361&interval=div%7Csplit&filter=split&frequency=1d Its frustrating. My last option was to get the dividends history of the stock and add back to the adjusted price to compute the total return for a select stock for the period."
Don't ever quantify a stock's preference/performance just based on the dividend it is paying out Volatility defined by movements in the the stock's price, affected by factors embedded in the stock e.g. the corporation, the business it is in, the economy, the management etc etc. Apple wasn't paying dividends but people were still buying into it. Same with Amazon, Berkshire, Google. These companies create value by investing their earnings back into their company and this is reflected in their share prices. Their earnings create more value in this way for the stockholders. The holding structures of these companies also help them in their motives. Supposedly $100 invested in either stocks. For keeping things easy, you invested at the same time in both, single annual dividend and prices more or less remain constant. Company A: $5/share at 20% annual dividend yield.  Dividend = $20 Company B: $10/share at 20% annual dividend yield  Dividend = $20 You receive the same dividend in both cases. Volatility willn't affect you unless you are trading, or the stock market tanks, or some very bad news comes out of either company or on the economy. Volatility in the long term averages out, except in specific outlier cases e.g. Lehman bankruptcy and the financial crash which are rare but do happen. In general case the %price movements in both stocks would more or less follow the markets (not exactly though) except when relevant news for either corporations come out. The biggest issue with Yahoo Finance is the recent change to the API in May. The data is good quality, includes both dividend/split adjusted and raw prices, but it's much more difficult to pull the data with packages like R quantmod than before.  Google is fine as well, but there are some missing data points and you can't unadjust the prices (or is it that they're all unadjusted and you can't get adjusted? I can't recall). I use Google at home, when I can't pull from Bloomberg directly and when I'm not too concerned with accuracy.  Quandl seems quite good but I haven't tried them. There's also a newer website called www.alphavantage.co, I haven't tried them yet either but their data seems to be pretty good quality from what I've heard. Do you realise that the examples you have given are for stock splits not for dividends, that is why the date payable is before the ex-date for the split. The payments for the split occur on 30th June and the first day the stock trades with the new split is on the next trading day, being the ex-date, 1st July. For implied volatility it is okey to use Black and scholes but what to do with the historical volatility which carry the effect of past prices as a predictor of future prices.And then precisely the conditional historical volatility.i suggest that you must go with the process like, for stock returns  1) first download stock prices into excel sheet 2) take the natural log of (P1/po) 3) calculate average of the sample  4) calculate square of (X-Xbar) 5) take square root of this and you will get the standard deviation of your required data. What you're referring to is the yield.  The issue with these sorts of calculations is that the dividend isn't guaranteed until it's declared.  It may have paid the quarterly dividend like clockwork for the last decade, that does not guarantee it will pay this quarter.   Regarding question number 2.  Yield is generally an after the fact calculation.  Dividends are paid out of current or retained earnings.  If the company becomes hot and the stock price doubles, but earnings are relatively similar, the dividend will not be doubled to maintain the prior yield; the yield will instead be halved because the dividend per share was made more expensive to attain due to the increased share price.   As for the calculation, obviously your yield will likely vary from the yield published on services like Google and Yahoo finance.  The variation is strictly based on the price you paid for the share.  Dividend per share is a declared amount.  Assuming a $10 share paying a quarterly dividend of $0.25 your yield is: Now figure that you paid $8.75 for the share. Now the way dividends are allocated to shareholders depends on dates published when the dividend is declared.  The day you purchase the share, the day your transaction clears etc are all vital to being paid a particular dividend.  Here's a link to the SEC with related information: https://www.sec.gov/answers/dividen.htm I suppose it goes without saying but, historical dividend payments should not be your sole evaluation criteria.  Personally, I would be extremely wary of a company paying a 40% dividend ($1 quarterly dividend on a $10 stock), it's very possible that in your example bar corp is a more sound investment. Additionally, this has really nothing to do with P/E (price/earnings) ratios. Adjusting for a market change from day to day, the dividend should have no impact on you. Your X shares time $Y should be nearly identical right after that dividend hits the account.  And within the 401(k) or IRA for that matter, the accounting doesn't matter most of the time. Outside a retirement account, you need to pay tax on the dividend, and add the newly purchased shares' cost to your cost basis. I am mostly interested in day to day records, and would like the data to contain information such as dividend payouts, and other parameters commonly available, such as on : http://finviz.com/screener.ashx ... but the kind of queries you can do is limited. For instance you can only go back two years. "If a stock is trading for $11 per share just before a $1 per share dividend is declared, then the share price drops to $10 per share immediately following the declaration. If you owned 100 shares (valued at $1100) before the dividend was declared, then you still own 100 shares (now valued at $1000). Generally, if the dividend is paid today, only the owners of shares as of yesterday evening (or the day before maybe) get paid the dividend. If you bought those 100 shares only this morning, the dividend gets paid to the seller (who owned the stock until yesterday evening), not to you. You just ""bought a dividend:"" paying $1100 for 100 shares that are worth only $1000 at the end of the day, whereas if you had just been a little less eager to purchase right now, you could have bought those 100 shares for only $1000. But, looking at the bright side, if you bought the shares earlier than yesterday, you get paid the dividend.  So, assuming that you bought the shares in timely fashion, your holdings just lost value and are worth only $1000.  What you do have is the promise that in a couple of days time, you will be paid $100 as the dividend, thus restoring the asset value back to what it was earlier.  Now, if you had asked your broker to re-invest the dividend back into the same stock, then, assuming that the stock price did not change in the interim due to normal market fluctuations, you would get another 10 shares for that $100 dividend making the value of your investment $1100 again (110 shares at $10 each), exactly what it was before the dividend was paid. If you didn't choose to reinvest the dividend, you would still have the 100 shares (worth $1000) plus $100 cash. So, regardless of what other investors choose to do, your asset value does not change as a result of the dividend.  What does change is your net worth because that dividend amount is taxable (regardless of whether you chose to reinvest or not) and so your (tax) liability just increased." "In addition to the other answers it's also noteworthy that the stock exchanges themselves adjust the price quotes via their ex-div mechanism.  All limit orders present in the book when the stock goes ex-div will be adjusted by the dividend. Which means you can't even get ""accidentally"" filled in the very unlikely case that everyone forgot to adjust their quotes." "Good observation. In fact, the S&P index itself is guilty of not including dividends. So when you look at the index alone, the delta between any two points in time diverges, and the 20 return observed if one fails to include dividends is meaningless, in my my humble opinion. Yahoo finance will let you look at a stock ticker and offer you an ""adjusted close"" to include the dividend effect." http://finance.yahoo.com/q/hp?s=EDV+Historical+Prices shows this which matches Vanguard: Mar 24, 2014  0.769 Dividend Your download link doesn't specify dates which makes me wonder if it is a cumulative distribution or something else as one can wonder how did you ensure that the URL is specifying to list only the most recent distribution and not something else. For example, try this URL which specifies date information in the a,b,c,d,e,f parameters: http://real-chart.finance.yahoo.com/table.csv?s=EDV&a=00&b=29&c=2014&d=05&e=16&f=2014&g=v&ignore=.csv One big difference:  Interest is contracted.  They can change the rate in the future but for any given time period you know what you're going to get. Dividends are based on how the company did, there is no agreed-upon amount. "Almost every online datasources provide historical prices on given company / index's performance; from this, you can easily calculate ""standard deviation"" by yourself. With that said, standard deviation presumes a fixed set of data. Most public corporations have data spanning multiple decades, during which a number of things have changed: For these reasons, I have doubts on simplistic measures, such as ""standard deviation"" measuring any reality on the underlying vehicle. Professional investors usually tend to more time-point data, such as P/E ratio." "The Securities Industry and Financial Markets Association (SIFMA) publishes these and other relevant data on their Statistics page, in the ""Treasury & Agency"" section. The volume spreadsheet contains annual and monthly data with bins for varying maturities. These data only go back as far as January 2001 (in most cases). SIFMA also publishes treasury issuances with monthly data for bills, notes, bonds, etc. going back as far as January 1980. Most of this information comes from the Daily Treasury Statements, so that's another source of specific information that you could aggregate yourself. Somewhere I have a parser for the historical data (since the Treasury doesn't provide it directly; it's only available as daily text files). I'll post it if I can find it. It's buried somewhere at home, I think." Yahoo provides dividend data from their Historical Prices section, and selecting Dividends Only, along with the dates you wish to return data for. Here is an example of BHP's dividends dating back to 1998. Further, you can download directly to *.csv format if you wish: http://real-chart.finance.yahoo.com/table.csv?s=BHP.AX&a=00&b=29&c=1988&d=06&e=6&f=2015&g=v&ignore=.csv