When attempting to determine the historical price of a stock over a long period of time, such as 10 years, you will need to make a number of decisions about what kind of data you will admit. The price of a company's stock can be measured in a number of ways, such as the day-to-day and the year-to-year price. For computing the midpoint, it's often best to use day-end prices.
Collect your data. The most important step in computing the midpoint of a company's stock price is to make sure that the data you have is accurate. The best place to find data on a company's historical stock price is from its investor-relations office. In some cases, however, you will have to check another source, such as a brokerage or a newspaper or from Internet sites such as Google and Yahoo.
Pick your values. From this data, pull the day-end prices for the company's stock over the last 10 years. If you have a spreadsheet program and you are able to obtain the data electronically, then you can save yourself time by inputting the numbers this way rather than by hand.
Order the values. After you have identified all of the day-end prices for the stock over the last decade, place them in order, beginning from lowest and ending with highest. This can be extremely difficult to do by hand, as you are dealing with several thousand numbers. However, this is relatively easy with a spreadsheet program that is able to sort data.
Take the middle number. If you have an odd number of prices, then you should select the number that falls in the very middle of the sequence. For example, if you have 2,501, you should examine the 1251 number in the sequence. If you have two numbers, then average them. This will provide you with your midpoint.
- The price of a stock will often not just fluctuate over a decade, but may undergo several splits or reverse stock splits. When this happens, the price of the stock will either rise or fall in proportion to the size of the split. You will need to factor these splits into your calculations. For information on historical splits, consult the same source from which you acquired the data.
- "Investing For Dummies"; Eric Tyson; 2008