Why Historical Stock Prices Differ Across Data Providers
Summary
The document examines why historical prices for the same listed stock can differ across data providers, using a London Stock Exchange example. It reports that separate trading platforms may contribute different kinds of observations: some daily summaries use actual trades, while others may use bid and ask midpoints. A security traded across multiple platforms can therefore have different reported open, high, low, and close values depending on the feed’s construction.
It also identifies other sources of divergence, including trade-condition filters, time-period definitions, cross-exchange consolidation rules, corporate-action adjustments, and supplier corrections or errors. A separate response notes that thin trading and problems in a provider’s chart or historical data may contribute, while another points to differences in split and dividend adjustment policies. These are plausible diagnostic avenues rather than a resolution of the specific quoted prices. The practical lesson is to establish what each provider’s fields include and how its historical series is adjusted before comparing or using the data.
Key ideas
- Different exchange platforms may report trade prices or quote midpoints in daily summaries.
- Open, high, low, close, and volume figures depend on included trades, quotes, time windows, and condition codes.
- Consolidated feeds can apply different rules to activity across exchanges.
- Corporate-action adjustments and later corrections can change historical price series.
- Low liquidity or provider data issues may explain some discrepancies, so the specific cause should be checked with the source.
Tags
Full text
# Why are there stock price inconsistencies between Yahoo Finance, Google, and other data providers? # Why are there stock price inconsistencies between Yahoo Finance, Google, and other data providers? For example, look up the London Stock Exchange stock CloudBuy PLC (CBUY) - The closing price on 7th June 2017 is different among data providers - 1) Google search the ticker and evaluate the price on chart: 2.88GBX 2) London Stock Exchange - search stock on website: 3.75GBX Anyone got any clues as to why there are these inconsistencies because I'm stumped. ## Answer by Richard at NorgateData (score 1) https://quant.stackexchange.com/a/39621 Although the London Stock Exchange is an exchange we don't cover in our services, when we were researching this exchange for coverage viability several years back we observed some interesting points that are relevant to this question. At that time, we purchased/subscribed to several vendors' data. Multiple platforms on one exchange The separate trading platforms used by the London Stock Exchange each had different price reporting. For example, the electronic order book-based platforms reported actual trades in the daily OHLC summaries but the market-maker-based platforms were reporting midpoint of the bid/ask. Where a stock traded on multiple platforms there were significant discrepancies in the OHLC. The following comments relate to data discrepancies in general: Trades/Quotes It is important that you know exactly what the open, high, low, close and volume represent. i.e. which trades (or quotes) are used, what time periods are used and which condition code(s) are excluded/incorporated. - e.g. consider the effect of block trades, multi-leg trades, cancelled/busted trades etc. Multi-exchange trading With cross-border/cross-exchange trading also available for some securities, if you are looking at consolidated/combined trading feeds, you need to determine which rules are in place for such trades too. Historical data adjustments Historical data can be adjusted for various corporate events such as stock splits, spin-offs (de-mergers), stock dividends, special dividends, special distributions, capital distributions, normal dividends, distributions in a currency other than the trading currency, events that give the holder a choice of multiple options etc. There are often different interpretations for the surviving entity of spin-offs/de-mergers too. Errors Lastly, it may just be data error(s) made by the data supplier (e.g. corporate actions that have subsequently been changed/cancelled) Summary Discrepancies are commonplace. Ask your provider how they handle all of the above if it is not documented. ## Answer by IKnowNothing (score 0) https://quant.stackexchange.com/a/39612 You certainly ask the right question ... "got any clues". Yes, some clues are that free market data has no warranties but more importantly CBUY has low volume so that could be a reason. There's one strange thing on https://finance.google.com/finance?q=cbuy where the chart x axis shows Wed Jun 7 2017. But when hovering over the close of that day, the upper left date shows April 17, 2018 15:30 Price 3.90. When I move the slider a bit to the left with a month view, the dates are daily but moving it slightly to the right gives 'intraday' bars. Could be just a data problem with CBUY on Google. This sites shows 3.76 ... https://www.tradingview.com/chart/?symbol=LSE:CBUY ## Answer by Quinton Pike (score 0) https://quant.stackexchange.com/a/41738 A lot of the historic data is adjusted for stock splits. Some sites also adjust the data for dividends. This can cause different prices on different sites.
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