In the legacy versions of Compustat, only a company level identifier was available, and any security data came from the most representative issue of the company. The CRSP CCM database now links CRSP PERMNO to both GVKEY and Compustat’s new security identifier, IID. By doing so, additional Compustat issues are identified and a CRSP PERMNO can link to Compustat data even when it is not the primary security.
Consider the following in order to access the new security level link data.
- Additional security links allow multiple PERMNOs of the same company to link to the sampe company level data. Users must be aware that the same company data can be retrieved in multiple ways.
- The PERMCO link is no longer needed since a secondary security can link directly between CRSP and Compustat. PERMCO can still be used to find other securities when no direct link is found.
- Security level links are available only during the range of Compustat security data. In some cases, Compustat security data are not available as far back as company data. In others, there may be gaps of security data within a company range. CRSP fills in the available Compustat company data range so at least one link record covers all time periods in the range. If no securities are available during a range, a dummy security is generated for purposes of the link. These dummy securities always have an IID ending with X.
- CRSP assigns a LINKPRIM market to all link records, based on the Compustat PRIMISS marker, which is used to identify the primary security for the company at any given time. LINKPRIM values are:
- P if marked by Compustat as the primary issue
- C if marked by CRSP as the primary issue at a time when Compustat marks no securities or multiple securities.
- CRSP supports an acess option of primary PERMNO, or ppermno, which restricts links to only those marked primary.
- The legacy CST format databases remain based on the old company-based links, thus using only the rows marked as primary.