A split does not change company value
A stock split divides one share into several. In a 4-for-1 split, a shareholder ends up with four times as many shares and each share trades at roughly a quarter of the price. The company's total value and each shareholder's stake stay the same; only the unit changes. Combining several shares into one is called a reverse split, and in the US it is sometimes done by companies whose price has fallen sharply, for reasons such as exchange listing requirements. A Korean example is Samsung Electronics, which carried out a 50-for-1 split in 2018 and saw its per-share price drop accordingly. Well-known large US tech companies have also split several times.
What a split does to the chart
If you plot unadjusted prices, the split day looks like the stock suddenly fell to a fraction of its value. Shareholders did not actually lose anything, yet the chart shows what looks like a crash. That is why most charts display adjusted prices, recalculating pre-split prices by dividing them by the split ratio. This connects the chart smoothly, but past prices no longer match the numbers that actually traded at the time. If a price quoted in news from years ago differs from today's chart on the same date, a split in between is usually the reason.
How dividends change the chart
The right to a dividend goes to whoever holds the stock by a set date. The day that right drops off is the ex-dividend date, and the stock tends to open lower by roughly the dividend amount in theory, since cash leaving the company reduces the share's value. In practice the open also reflects other news and order flow, so it rarely moves by exactly the dividend. In the US, a shorter settlement cycle means the ex-dividend date and the record date now usually fall on the same day, while in Korea the ex-dividend date typically comes one day before the record date because of its settlement cycle. Check the company's filings for the exact schedule.
Adjusted prices come in more than one kind
"Adjusted price" means slightly different things to different data providers. The most common kind reflects only splits and reverse splits, while another also reflects dividends by lowering past prices. A chart built from dividend-adjusted prices looks closer to total return, price gains plus dividends, so the gap with an unadjusted chart grows for high-dividend stocks. If the same stock shows different past prices or returns on two screens, suspect a difference in adjustment method first.
- Raw price: exactly what traded at the time
- Split-adjusted: reflects split and reverse-split ratios only
- Dividend-adjusted: also lowers past prices for dividends
- Check whether volume is adjusted by the split ratio too
Common misreadings caused by adjusted prices
Adjusted prices exist to keep a chart continuous, but they create a few illusions. When you say there was support or resistance at a certain level in the past, that level is an adjusted number, not the one traders saw at the time. Very old prices showing up as tiny numbers can make a stock feel like it was extremely cheap back then, when that is just the result of repeated splits. Dividend-adjusted data can change past values every time a new dividend is paid, so it may not match numbers you wrote down earlier. For long periods, a log scale makes percentage changes easier to compare.
Care in backtests and return calculations
When testing a strategy or calculating returns on historical data, which price you use can change the result a lot. Raw prices create a fake crash on the split day and trigger stop-loss rules for no real reason. Ignoring dividends understates the performance of high-dividend stocks, while computing trade signals from dividend-adjusted prices can place signals at levels that differ from what the chart actually showed that day. Make it a habit to check which data a result is based on.
Checking with this site's live tools
Running the same stock over a long period in the stock strategy backtester shows how much the data window and conditions affect the result. The dividend calculator lets you work out accumulated dividends separately, and placing a high-dividend stock beside a low-dividend one in the stock comparison tool helps you sense the difference that comes from comparing price charts alone. Read each tool's notes first to see which price basis it uses.
Summary and caution
Splits and reverse splits change the unit, not the value, but they force past prices on a chart to be recalculated. Dividends adjust price on the ex-dividend date and, depending on the data, may be reflected in past prices. When comparing charts or reviewing past performance, first check which adjusted price you are looking at. Keep in mind too that split news by itself does not make a company worth more. This article is not investment advice and does not recommend trading any stock.
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