What does Polygon do with delisted tickers?

Survivorship bias refers to the tendency to focus on the performance of existing stocks or funds without considering those that have failed. To avoid this bias, our market data includes companies that have been delisted from the exchanges and is stored as it occurred on that date.

Additionally we have a Ticker Events Endpoint that displays a ticker symbol's full history, including changes such as mergers, acquisitions, delistings, and ticker symbol changes.