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How do I find an historical stock quote?

Yahoo!Finance has an historical stock quote search, found at their stock research center page.

Here's a short course on how to use the historical quote tool. If you need a specific date -- say June 2, 1997-- enter June 1, 1997 as the start date, and June 3, 1997 as the end date. Then chose "Daily" prices.

After clicking "Get Prices," you should end up with opening, high, low and close, along with the adjusted close price for those dates:

historical_quotes.gif

Adjusted close is the closing price adjusted for stock splits over time. Avoid using the adjusted close price for historical valuation purposes, as it is mainly for making assessments of stock performance. There is a great explanation of that at Investopedia. The adjusted price can be a great tool if you want to see what the appreciated value of a stock is, and you can read more about that further on...

For Development Research purposes, we either value stock information at the current value or the historical value, depending on the date of the information we have about stock ownership. If we know that a certain number of shares were owned on a certain date, but if it's unclear when or if the stock was sold, researchers will often value the stock using the market closing price of the known date of ownership (record date). But if we suspect that the stock could still be owned, it is useful to know what the stock would be worth at the current price. But read on!

This is where it could get tricky. You really need to determine if the stock has split since the record date, i.e. the date when the stock was held. If the stock has greatly appreciated over time, and the company has split the stock, you could grossly underestimate the value of stock holdings if you don't take those splits into account. A good rule of thumb is to look at the "adjusted close price" on the historical price chart, and if it's different from the "close price," then the stock has likely split.

One source of splits can be found in the charts which Yahoo!Finance provides. When you get a stock quote from Yahoo!Finance, you'll see a thumbnail chart of stock price at the right of the screen. Click just below that on "max" for a chart of the maximum number of years, and you'll get a big stock chart with most or all of the stock splits listed below it.

Yahoo!'s chart (YHOO) shows the following list of stock splits:

Splits:02-Sep-97 [3:2], 03-Aug-98 [2:1], 08-Feb-99 [2:1], 14-Feb-00 [2:1], 12-May-04 [2:1]

So, how would I use this information? Well, let's say that someone held 1,000 shares of YHOO on June 2, 1997. You could look at this two ways. One, what was the value of the stock on 6/2/97? Two, if they have not sold the stock, what would it be worth today?

In the first case, we use the historical quote tool to determine that the stock price on 6/2/97 was $33.13 per share. So 1,000 shares on 6/2/97 were worth a total of $33,130.

In the second case -- to find today's value of those 1,000 shares -- we need to take the splits into account. On 9/2/97 the stock split three-for-two (3:2). That's 1,000 times 3/2, or 1,500 shares. On 8/3/98, those 1,500 shares split two-for-one, so the stockholder then had 3,000 shares. On 2/8/99 they split two-for-one again, so there would then be 6,000 shares. On 2/14/00 they doubled again (12,000 shares), and again on 5/12/04 (24,000 shares). Yesterday's YHOO market close price was $33.70 per share, so those 24,000 shares were worth $808,800 on 10/18/2005.

Shortcut: Use adjusted close price

For the mathematically inclined, one shortcut to determining the value after splits is to use the adjusted close price from the historical quote tool. For June 2, 1997, it lists a market close price of 33.13 and an adjusted close price of 1.38. Divide 33.13 by 1.38 and you come up with 24.007. Multiply by 1,000 and you come pretty close to the 24,000 share figure determined above. Or you could divide 1.38 by 33.13, which gives you 0.041654. Divide $33,130 by 0.041654, and you get $795K, which is very close to the $808K figure above.