How to calculate the closing price percentage change for a stock?
The previous day's close on Thursday 10th October was 5,000.00 The close on Friday 11th October is 5,025.92 So the gain on Friday was 25.92 (5025.92 - 5000) or 0.52% (25.92/5000 x 100%). No mystery!
I sell a put for a strike price at the market. The stock rises $50 over the next couple months. I've gotten the premium, but lost the rest of the potential gain, yet had the downside risk the whole time.  There's no free lunch.  Edit - you can use a BS (Black-Scholes) calculator to create your own back testing. The calculator shows a 1% interest rate, 2% yield, and 15% volatility produce a put price almost identical to the pricing I see for S&P (the SPY ETF, specifically) $205 put. No answer here, including mine, gave any reference to a study. If one exists, it will almost certainly be on an index, not individual stocks. Note that Jack's answer referencing PUTX does exactly that. The SPY ETF and it put options. My suggestion here would, in theory, let you analyze this strategy for individual stock options as well.  For SPY - With SPY at 204.40, this is the Put you'd look at -  12 times the premium is $33.36 or 16% the current price. The next part of the exercise is to see how the monthly ups and downs impact this return. A drop to $201 wipes out that month's premium.  It happens that it now March 18th, and despite a bad start to the year, we are at break-even YTD. A peek back shows In Dec you picked up $2.87 premium, (1.4% the current price then) but in Jan, it closed for a loss of $12. Ouch. Now, if you started in January, you'd have picked up 2 month's premiums and today or Monday sell the 3rd. You'd have 2.8% profit so far, vs the S&P break even.  Last, for now, when selling a naked put, you have to put up margin money. Not sure how much, but I use percent of the value of underlying stock to calculate returns. That choice is debatable, it just keeps percents clean. Else you put up no money and have infinite return. It will depend largely on your broker what type of stop and trailing stop orders they provide. Saying that, I have not come across any brokers yet that offer limit orders with trailing stop orders.  Unlike a standard stop order where you can either make it a market stop order or a limit stop order, usually most brokers have trailing stop orders as market orders only, where you can either set the trailing stop to be a dollar value or percentage from the most recent high. Remember also, that trailing stop orders will be based on the intra-day highs and not the highest closing price. That means that if the share price spikes up during the day your trailing stop will move up, and if the price then spikes down you may be stopped out prematurely, after which the price might rally again. For this reason I try to base my trailing stops on the highest closing price by using standard stop loss orders and moving it up manually after the close of trade if the share price has closed at a new high. This takes a few minutes each evening (depending on how many stocks you have to check and adjust the stops for) but gives you more control. Using this method will also enable you to set limit orders attached to your stop loss triggers, and you won't have to keep your trailing too close to the last high price thus potentially causing you to get stopped out prematurely. Slightly off track but may be handy if you set profit targets, my broker has recently introduced Trailing Take Profit Orders. The way it works is, say you have a profit target of 50%, so you buy at $2 and want to take profits if the price reaches $3, you could set your Trailing Take Profit Trigger at say $3.10 or above and set a Trail by Amount of say $0.10. So if the price after hitting $3.10 falls to $3.00 you will be stopped out and collect your profits. If the price moves up to $3.30 and then falls to $3.20, you will be stopped out at $3.20 and make some extra profits. If the price continues going up the Trailing Take Profit will continue to move up always $0.10 below the highest price reached. I think this would be a very useful order if you were range trading where you could set the Trailing Take Profit trigger near recent resistance so you can get out if prices start reversing at or around the resistance, but continue profiting if the price breaks through the resistance. One thing to keep in mind when calculating P/E on an index is that the E (earnings) can be very close to zero.  For example, if you had a stock trading at $100 and the earnings per share was $.01, this would result in a P/E of 10,000, which would dominate the P/E you calculate for the index.  Of course negative earnings also skew results. One way to get around this would be to calculate the average price of the index and the earnings per share of the index separately, and then divide the average price of the index by the average earnings per share of the index. Different sources calculate these numbers in different ways.  Some throw out negative P/Es (or earnings per share) and some don't.  Some calculate the price and earnings per share separate and some don't, etc... You'll need to understand how they are calculating the number in order to compare it to PEs of individual companies. Ok you're looking at this in a very confusing way. First, as said by CapitalNumb3rs, the dividend yield is the dividends paid in the year as a percent of the stock price. Given this fact then if the stock price moves down and the dividend stays the same then the yield increases. Company's don't usually pay out on a yield basis, that's mostly just a calculation to measure how strong a dividend is. This could mean either A. The stock is underpriced and will rise which will lower the yield to a more normal level or B. the company is not doing as well and eventually the dividends will decrease to a point where the yield again looks more normal.   Second off let's look at it in a more realistic way that still takes into account your assumptions:  **YEAR 1** 1. Instead of assuming buying 35% let's put this into a share amount. Let's say there are 1,000,000 shares so you just bought 350k shares for $700k. You paid a price of $2/share. Let's assume the market decides that's a fair price and it stays that way through the end of year 1. This gives us a market capitalization of $2 million.  2. The dividend paid out at year 1 is $60k so you could calculate on a per share basis which would be a dividend of $60k / 1 million shares or a $0.06 dividend per share. Our stock price is still at $2.00 so our yield comes out to $0.06 / $2.00 or 3.0%  **YEAR 2** Assuming no additional shares issued there are still a total of 1 million shares outstanding. You owned 350k and now want to purchase another 50k (5% of outstanding share float). The market price you are able to purchase the 50k shares at has now changed which means that share price is now valued at $1.50 / share. We have a dividend paid out at $100k, which comes out to a dividend per share of $0.10. We have a share value of $1.50 and the $0.10 dividend per share giving us a new yield of 6.66%.   **CONCLUSION:** There are many factors that can cause a company's stock price to fluctuate, some of it is hype based but some of it is a result of material changes. In your case the stock went down 25%. In most scenarios where a stock would have that much decline it would likely either not have been paying a dividend in the first place or would maybe not be paying one for much longer. Most companies that pay dividends are larger and more mature companies with a steady, healthy and predictable cash flow. Also most companies that are that size would not trade a stock under $3.00, I know this is just an example but the scenario is definitely a bit extreme in terms of the price drop and dividend increase. Again the yield is just a calculation that depends on the dividend that is usually planned in advance and the stock price that can fluctuate for many reasons. I hope this made everything more clear and let me know if you have any other questions. "This is the same answer as for your other question, but you can easily do this yourself: ( initial adjusted close / final adjusted close ) ^ ( 1 / ( # of years sampled) ) Note: ""# of years sampled"" can be a fraction, so the one week # of years sampled would be 1/52. Crazy to say, but yahoo finance is better at quick, easy, and free data.  Just pick a security, go to historical prices, and use the ""adjusted close"". money.msn's best at presenting finances quick, easy, and cheap." It seems like you want to compare the company's values not necessarily the stock price.  Why not get the total outstanding shares and the stock price, generate the market cap.  Then you could compare changes to market cap rather than just share price. "Yahoo's ""Adj Close"" data is adjusted for splits, but not for dividends. Despite Yahoo's webpage's footnote saying  *Close price adjusted for dividends and splits. we can see empirically that the ""Adj Close"" is only adjusted for splits. For example, consider Siemens from Jan 27, 2017 to Mar 15, 2017: The Adj Close adjusts for splits: On any particular day, the ""Adj Close"" is equal to the ""Close"" price divided by the cumulative product of all splits that occurred after that day. If there have been no splits after that day, then the ""Adj Close"" equals the ""Close"" price. Since there is a 2-for-1 split on Mar 14, 2017, the Adj Close is half the Close price for all dates from Jan 27, 2017 to Mar 13, 2017. Note that if Siemens were to split again at some time in the future, the Adj Close prices will be readjusted for this future split. For example, if Siemens were to split 3-for-1 tomorrow, then all the Adj Close prices seen above will be divided by 3. The Adj Close is thus showing the price that a share would have traded on that day if the shares had already been split in accordance with all splits up to today. The Adj Close does not adjust for dividends: Notice that Siemens distributed a $1.87 dividend on Feb 02, 2017 and ~$3.74 dividend on Jan 30, 2017. If the Adj Close value were adjusted for these dividends then we should expect the Adj Close should no longer be exactly half of the Close amount. But we can see that there is no such adjustment -- the Adj Close remains (up to rounding) exactly half the Close amount: Note that in theory, the market reacts to the distribution of dividends by reducing the trading price of shares post-dividend. This in turn is reflected in the raw closing price. So in that sense the Adj Close is also automatically adjusted for dividends. But there is no formula for this. The effect is already baked in through the market's closing prices." I don't know what restrictions are put on the average employee at your company. In my case, we were told we were not permitted to either short the stock, or to trade in it options.  That said, I was successful shorting the exact number of shares I'd be buying at the 6 month close, the same day the purchase price would be set. I then requested transfer of the stock purchase to my broker where the long and short netted to zero.  The return isn't 15%, it's  100/85 or 17.6% for an average 3 months they have your money. So do the math on APR. (Higher if the stock has risen over 6 months and you get the lower price from 6 months prior.) My method was riskless, as far as I am concerned. I did this a dozen times. The stock itself was +/- 4% by the time the shares hit, so in the end it was an effort, mostly to sleep better. I agree with posts suggesting the non-zero risk of a 20% 4 day drop.