Adjusted vs Raw Stock Prices: Preserve the Provider Definition

Separate price adjustments, corporate actions and total-return assumptions before comparing historical series.

Declare the OHLC basis

A provider may expose raw OHLC, split-adjusted OHLC, adjusted close or a different corporate-action convention. Read the endpoint definition. A field called adjustedClose does not establish that the other four prices use the same basis.

Do not manufacture an adjustment factor

The local inspector checks the supplied prices and their high/low relationship. It does not rescale raw OHLC from an adjusted-close ratio or infer split/dividend events. Such a conversion can be wrong when the source fields follow different conventions.

Treat a large move as an investigation

A close-to-close warning compares consecutive usable unique-date observations. It can cross a gap and is not labelled a one-day return. A genuine price move, a corporate action, a currency change or a data error can all require different treatment. No automatic correction is made.

Keep performance assumptions separate

A split-adjusted price path alone is not a total-return series. Cash distributions, reinvestment, transaction costs and financing need explicit handling. Use the backtesting catalogue for that distinct task and keep the original source’s adjustment policy with the input file.