I'm a web developer responsible for creating a website that has a section which contains the stock information of a certain company. This information is retrieved through an API which a stock exchange company provides (Tadawul All Share (TASI))

I realized that for some days the prices shown in the Historical Data chart are different from any of the prices contained in Historical Data table for example here are the data for a specific day ( 20-05-2018 )

yet the price for that day in the historical data chart is different from any of the data provided (17.1)

My question is: what does the price in the historical chart refer to. I realize most of the prices in the historical chart match the 'close price'.. but as there are many times that the price is much different from the close price, I want to make sure.

and if it refers to the close price what could be the reason for it to be different from the close price for some days? is it an error?

1 Answer 1


If your data point and your graph come from the same service then there's some bad data involved. If not, a legitimate explanation may be that one of them is adjusting historical price data to remove gaps caused by stock splits, dividends, and distributions. An adjusted chart and an unadjusted will look different.

An extreme example would be a stock that undergoes a stock split. If a 2:1 split occurs, price suddenly drops 50%. Since a split does not result in any gain or loss of shareholder value, the price of all data prior to the split is halved. This adjustment is also done for dividends and distributions because these too do not result in any gain or loss of shareholder value.

This adjustment of data is relevant to those who use Technical Analysis. Unadjusted data could trigger false signals when in fact no market forces were in play (share price increasing or decreasing due to buying and selling).

One drawback of adjusted data is that once it has been done, it cannot be used to determine the actual buy or sell price for a stock at some point in the past.

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