Adjusted vs. Unadjusted Stock Prices: Comparing Charts Across Stock Splits
Adjusted prices account for events such as stock splits to make historical prices comparable. Learn when to use each series and why dividend adjustments change return calculations.
Unadjusted prices are the prices at which shares traded at the time. Adjusted prices restate historical comparisons for corporate actions such as splits. Adjustment coverage varies by data provider, so an adjusted series should not automatically be read as a total return that includes dividends.
When the share count changes, the per-share price changes too
A stock split divides the same ownership interest into more shares. Assuming unchanged market value immediately after the split, doubling the share count halves the per-share price. Connecting only unadjusted prices can make it appear that half the value disappeared, so charts can adjust historical prices by the split ratio to preserve continuity. This does not mean you could actually have placed orders at those lower prices in the past. To reconstruct historical transactions and book amounts, use unadjusted prices together with the corporate actions.
Match the adjustment method to your analysis
A series adjusted only for splits, one also reflecting cash dividends, and one additionally reflecting changes in shareholder rights produce different results. Read the documentation even if a column is labeled adjusted close. To calculate investment performance with dividends reinvested, verify that the data incorporate that assumption and do not add dividends again if they are already included. Conversely, with split-only adjustments, calculate cash dividend income separately. Even where documentation such as Nasdaq's labels the previous close as adjusted, do not infer the meaning of other price columns without checking.
Do not mix adjustment bases in indicator calculations
Calculating moving averages from adjusted closes while using unadjusted highs and lows misaligns the ranges around a split. Check whether volume uses pre-split share units or is restated on a post-split basis. In practice, keeping raw data and separately recording adjustment events, ratios, and effective dates makes provider differences easier to track. When asking whether a stock has regained a historical high, compare a series with consistent settings rather than an unadjusted historical peak with a current adjusted price. For verification, select a day on either side of a split and manually convert the shares held to check that changes in position value agree with the adjusted-price return. After switching providers, compare corporate-action dates before comparing the entire long-term chart. Recording that identically named columns can use different adjustments makes it easier to explain later changes in calculation results.
Worked example
Hypothetical example: Suppose a stock trades at KRW 50,000 before a five-for-one split and KRW 10,500 afterward. Restating the earlier price on the post-split basis gives KRW 10,000, so the price has risen 5%. Comparing the unadjusted prices and interpreting the change as a 79% decline ignores the increase in shares. An existing holding of 10 shares becomes 50, and its value changes from KRW 500,000 to KRW 525,000.
What to check
- Which events are adjusted for: splits, dividends, or both?
- Are prices and volume adjusted on a consistent basis?
- Have you avoided adding dividends that are already reflected in the data?
Sources and primary materials
This is educational material about research methods. For an actual company decision, verify the filings and primary sources for the relevant period.