Interpreting Split-Adjusted Historical Stock Prices

Summary

The document addresses a discrepancy between historical stock prices shown in a finance website interface and values in its downloadable data. The example shows an apparent inconsistency between daily high and low values and the displayed close, alongside different open, high, low, and adjusted-close figures in the downloaded file. The response attributes the discrepancy to a stock split and advises using adjusted close when calculating returns.

The key practical point is that raw prices and adjusted prices may be represented differently across data views, and corporate actions can make unadjusted historical prices unsuitable for return calculations. The brief answer does not explain the adjustment formula, identify the precise split mechanics, or assess the reliability of the provider's data generally. It therefore offers a useful basic diagnostic rather than a full guide to validating historical price series; users still need to check how a source handles splits and other distributions before comparing or modeling returns.

Key ideas

• A stock split can explain apparent inconsistencies among historical price fields.
• Adjusted close is the suggested price series for calculating historical returns.
• Data interfaces and downloadable files may show different adjusted or unadjusted values.
• The short explanation does not establish the provider's overall data reliability.

Tags

# How can I get reliable Yahoo Finance stock information?


# How can I get reliable Yahoo Finance stock information?












I've been trying to calculate returns for different stocks but using Yahoo Fiance Historical price data seems to be weird. For instance, looking up the March 5th 2012 Price for APPL on the online interface gives:

```
Open    High    Low     Close   Adj Close
77.92   78.21   75.14   533.16  76.17
```

This in itself doesn't make sense, why is the close so much higher than the high/low?

To add to my confusion if I download the csv it gives different numbers entirely (except for the close):

```
Open    High    Low     Close   Adj Close
545.42  547.48  526.00  533.16  69.08
```

Am I doing something wrong and if not where can I get somewhat accurate financial data?

## Answer by rbm (score 2)

https://quant.stackexchange.com/a/32819

You really care about the adjusted close. The difference you're seeing is caused by the stocks split, see e.g.

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