I want to chart the daily returns of a stock, and I'm using Yahoo finance data to download historic data. I was told to use Adjusted Close, but there seems to be an issue with this.
For ANTO.L, you can see that on 19 Jun 2006 there was a 5:1 split. The adjusted close reflected this, and went from 71.97 to 365.36. This of course skews my daily returns, as it represents a 400%+ return!
Should I be using adjusted close to calculate returns? It makes sense when considering dividends, but whenever there is a stock split there is then a huge skew. Is there something else I'm missing that I need to look into?
EDIT:
I think there's lots of examples of the same bad calculations. SRP.L shows the same for example. Problem is the Close is wrong, and the AdjClose is wrong, so I can't trust anything. Can anyone point me towards a good reliable free (or reasonably priced) provider of historic stock data, so I can use for comparisons?
Answer
Hmm, this table looks wrong. Here's what it should look like. After the most recent corporate action, the Close and Adjusted Close should be the same; only prices from before the most recent action should have a different Adjusted Close. Here's another example. I think Yahoo just has the wrong information.
If you wanted to derive your own adjustments for calculating returns, you'll need to know the date and nature of every corporate action. Then you'll fake the prices of the future rather than the prices of the past. Ie, you'll add back dividends and undo splits going forward. This is the opposite of what Yahoo is doing in their table; the reason for adjusting closes in the future is to prevent negative prices, which can happen if you subtract dividends from the values in the past. Once you have the adjusted prices, you can compute your returns without worry.
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