Link History Data

LINK Defined Structure

Native Link usage provides access to Compustat records, regardless of whether or not securities are in the CRSP universe. All Compustat data including index data, Canadian records, and off-exchange ranges that cannot be directly linked to CRSP Data are accessed using GVKEY, GVKEY.IID, and GVKEYX. The native link reads Compustat data as organized and identified by Compustat identifiers and can choose CRSP data appropriate to those records. Decisions on handling overlaps or soft links are left to the user.

Mnemonic Field Name Format
LINKDT

linkdt is a calendar date in YYYYMMDD format marking the first effective date of the current link. It is derived from the first or last date of a CRSP exchange listing, the date of a CRSP name change corresponding to the beginning or end of the link the rows of available Compustat data, or the date of a Compustat description change corresponding to the beginning or end of the link.

If a linkdt is derived from a last date, it will actually be the day after the last date. Since CRSP keeps link records for the entire Compustat history, if the Compustat history ends after the CRSP history, the linkdt of a row marking a no-link period can start the day after the CRSP delist date.

integer
LINKENDDT Last effective date of the link record. If the name represents current link information, the LINKENDDT is set to 99999999 integer
LPERMNO CRSP PERMNO link during link period. It is set to zero if there is no CRSP link during the range. integer
LPERMCO CRSP PERMCO link during link period. It is set to zero if there is no CRSP link during the range. integer
LIID Security identifier character
LNKTYPE Link type code. Each link is given a code describing the connection between the CRSP and Compustat data. Values are:
  • LC – Link research complete. Standard connection between databases.
  • LU – Unresearched link to issue by CUSIP
  • LX – Link to a security that trades on another exchange system not included in CRSP data.
  • LD – Duplicate link to a security. Another GVKEY/IID is a better link to that CRSP record.
  • LS – Link valid for this security only. Other CRSP PERMNOs with the same PERMCO will link to other GVKEYs.
  • LN – Primary link exists but Compustat does not have prices.
  • NR – No link available, confirmed by research
  • NU – No link available, not yet confirmed
character
LINKPRIM Primary issue marker for the link. Based on Compustat Primary/Joiner flag (PRIMISS), indicating whether this link is to Compustat’s marked primary security during this range.
  • 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.
character

LINKUSED Defined Structure

LINKUSED includes all of the fields in the link sturcture plus UGVKEY and USEDFLAG. Its number of rows exceeds that of the link structure because it has all link records of all GVKEYs with a match to a PERMNO, even those not used. USEDFLAG = 1 in LINKUSED is a subset of the available link records. It is loaded each time data are accessed in CRSP-Centric mode, such as for ts_print, TsQuery, or when C functions are run. The function builds a composite Compustat record from one or more Compustat GVKEYs and IIDs linked to a CRSP PERMNO. LINKUSED data are accessed using the composite PERMNO, APERMNO, or the Primary PERMNO, PPERMNO.

Mnemonic Field Name Internal Storage
ULINKDT ulinkdt is a calendar date in YYYYMMDD format marking the first effective date of the current link. It is derived from the first or last date of a CRSP exchange listing, the date of a CRSP name change corresponding to the beginning or end of the link the rows of available Compustat data, or the date of a Compustat description change corresponding to the beginning or end of the link. integer
ULINKENDDT Last effective date of the link record. If the name represents current link information, the ULINKENDDT is set to 99999999 integer
ULINKID Unique ID per link associated with PERMNO. This is used to join with range data in the LINKRANGE table that describes the data ranges applied from used GVKEYs. integer
UGVKEY GVKEY used in the link integer
UPERMNO CRSP PERMNO link during link period. It is set to zero if there is no CRSP link during the range. integer
UPERMCO CRSP PERMCO link during link period. It is set to zero if there is no CRSP link during the range. integer
UIID Used Security ID character
USEDFLAG Flag marking whether link is used in building composite record character
ULINKPRIM Primary issue marker for the link. Based on Compustat Primary/Joiner flag (PRIMISS), indicating whether this link is to Compustat’s marked primary security during this range.
  • 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.
character
ULINKTYPE Link type code. Each link is given a code describing the connection between the CRSP and Compustat data. Values are:
  • LC – Link research complete. Standard connection between databases.
  • LU – Unresearched link to issue by CUSIP
  • LX – Link to a security that trades on another exchange system not included in CRSP data.
  • LD – Duplicate Link to a security. Another GVKEY/IID is a better link to that CRSP record.
  • LS – Link valid for this security only. Other CRSP PERMNOs with the same PERMCO will link to other GVKEYs.
  • LN – Primary link exists but Compustat does not have prices.
  • NR – No link available, confirmed by research
  • NU – No link available, not yet confirmed
character

LINKRNG Defined Structure

CRSP generates a range table with information on the fiscal periods associated with each used link for each time series calendar frequency and keyset. This shows ranges in each of the fiscal and calendar calendars available in the CCM. This range table shows the ranges from the GVKEY for each type of time series data used to build the composite record for the PERMNO selected.

Mnemonic Field Name Format
RLINKID Linkused row identifier integer
RKEYSET Keyset applicable to range integer
RCALID Calendar applicable to range integer
RBEGIND Beginning time series range of link integer
RENDIND Ending time series range of link integer
RPREVIND Time series range immediately prededing the link integer
RBEGDT Beginning calendar range of link integer
RENDDT Ending calendar range of link integer
RPREVDT Ending calendar range preceding the link int(4)
RFISCAL_DATA_FLG Type of time series, C-calendar or F-fiscal. char(8)

CRSP-Centric Link Usage

Accessing Compustat data through ts-print and TsQuery is done through the CRSP-centric mode, meaning that the primary access key in this mode is CRSP PERMNO or PERMCO rather than GVKEY, as used in the Native Access mode. The CRSP identifiers are the access keys while the Compustat identifiers become attributes.

In CRSP-Centric mode a composite record is built using the CRSP Link reading one or more GVKEYs. All GVKEYS with some presence of the PERMNO in the link are accessed. A used-link history is built from these link records by identifying those that cover the ranges of Compustat data needed to link to the CRSP identifier. The USEDFLAG for time series items that are stored on a fiscal period basis, the link ranges are translated to a fiscal range. This translation simplifies the selection of fundamental data that are applicable to the range and allows for the creation of a composite Compustat record from the applicable ranges that correspond to a CRSP security.

Records in CRSP-Centric form are identical in layout to the native records, but use CRSP PERMNO as the effective key. The Compustat component identifiers – GVKEY, IID, and PRIMISS are available in a Link Used table in the CRSP records.

Using the CRSP-Centric view simplifies access when viewing Compustat data through CRSP. One drawback, however, is that only data considered a primary link to CRSP, applied using CRSP link rules, are available.

Accessing two separate GVKEYs from the Link table, see that both share a single PERMNO.

GVKEY = 011947
Link History
LINKDT LINKENDDT LPERMNO LPERMCO LIID LINKTYPE LINKPRIM
19820701 19860304 0 0 00X NR C
19860305 19890228 10083 8026 01 LU P
GVKEY = 015495
Link History
LINKDT LINKENDDT LPERMNO LPERMCO LIID LINKTYPE LINKPRIM
19880101 19890227  0 0 00X NU C
19890228 19930909  10083 8026 01 LC C
19930910 19990304  0 0 01 NR C

Using CRSP-Centric access in the USEDLINK table, access the composite history using the Primary PERMNO (LINKPRIM=P)

PERMNO = 10083
Link Used
LINKDT LINKENDDT GVKEY IID LINKID PERMNO PERMCO USEDFLAG LINKPRIM LINKTYPE
19820701 19860304  11947 00X 5 0 0 -1 C NR
19860305 19890228  11947 01 6 10083 8026 1 P LU
19880101 19890227 15495 00X 0 0 0 -1 C NU
19890228 19930909  15495 01 1 10083 8026 1 C LC
19930910 19990304 15495 01 2 0 0 -1 C NR
19990305 20051019 15495 01 3 86787  16430  -1 C LC
20051020 99999999  15495 01 4 0 0 -1 C NR