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, dividends, shares outstanding, and delisting information. A related identifier, PERMCO, denotes the permanent company number for the issuing entity. The CRSP Link Tableprovides mappings among PERMNO, PERMCO, ticker symbols, CUSIPs, and effective dates, to accommodate corporate actions and changes in securities over time.

PERMNOs are not market tickers and should not be assumed to be stable outside CRSP. New PERMNOs may be assigned when a security is created or significantly changed (for example, due to corporate actions or the issuance of a new security class). As a result, researchers often use the link table to bridge historical data and maintain consistent records for longitudinal analyses.

Access to PERMNO and related CRSP identifiers is restricted to licensed CRSP users. In practice, analysts reference PERMNOs to assemble long-run datasets for empirical studies, enabling consistent identification of securities across different datasets and time periods.