Why Adjusted Close May Match Across Different Download Ranges

Summary

The document asks whether a provider’s adjusted closing prices depend on the date range used to download a stock’s history. The author expects adjustments for dividends and splits to be anchored to the final date in each requested range, and compares overlapping data from a long and a shorter download. The observed adjusted prices match despite corporate actions during the overlap.

No explanation or confirmed rule is provided, so the comparison raises a data-handling question rather than establishing how the provider calculates adjustments. The result may depend on the data source’s adjustment methodology and whether historical values are revised. Researchers should check the provider’s documentation and compare overlapping observations when combining downloads; this brief exchange does not establish that matching prices will hold for other sources or dates.

Key ideas

• Adjusted closing prices can be compared across overlapping downloads with different start dates.
• The author reports matching adjusted prices in the overlap despite intervening dividends and a stock split.
• The document does not establish whether adjustment factors depend on the requested date range.
• Data users should verify the adjustment convention used by their particular provider.

Tags

# "Adj Close" data could be different in different data range?


# "Adj Close" data could be different in different data range?












I use `python DataReader` for getting past stock data.

I heard that `Adj Close` data could be different each other if data range is different between datas. This is because (as I know of) `Close` data is adjusted based on the LAST DATE of period.

For example,

> APPL1_data : 2010-01-01 ~ 2016-01-01 adj close data APPL2_data : 2014-01-01 ~ 2016-01-01 adj close data

But as I compare these datas by myself, both have same `Adj close` datas even though ex-dividend, stock split have happend during this period.

Did I miss something?

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