PERMNO
PERMNO stands for Permanent Number and is a unique identifier used in the CRSP (Center for Research in Security Prices) stock database to track a specific security over time. Each security issued on U.S. equity markets is assigned a PERMNO, which remains associated with that security across corporate actions, ticker changes, and delistings. The identifier helps researchers compile continuous time-series data despite changes in market symbol or exchange listing.
In CRSP, PERMNO is the primary key used to link data across modules, such as prices, returns,
PERMNOs are not market tickers and should not be assumed to be stable outside CRSP. New PERMNOs
Access to PERMNO and related CRSP identifiers is restricted to licensed CRSP users. In practice, analysts reference