Security Level Link Data Considerations
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 same 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 marker to all link records, based on the Compustat PRIMISS marker. PRIMISS is used to identify the primary security for the company at any given time. LINKPRIM values are:
- P=Primary, identified by Compustat in monthly security data.
- J=Joiner secondary issue of a company, identified by Compustat in monthly security data.
- C=Primary, assigned by CRSP to resolve ranges of overlapping or missing primary markers from Compustat in order to produce one primary security throughout the company history.
- N=Secondary, assigned by CRSP to override Compustat. Compustat allows a US and Canadian security to both be marked as Primary at the same time. For Purposes of the link, CRSP allows only one primary at a time and marks the others as N.
- CRSP supports an access 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.