wrds (version 0.0.1)

link_ccm: Get CRSP-Compustat linking table

Description

Downloads the CCM (CRSP-Compustat Merged) linking table that maps CRSP PERMNOs to Compustat GVKEYs with valid date ranges.

Usage

link_ccm(
  wrds,
  linktype = c("LC", "LU", "LS"),
  linkprim = c("P", "C"),
  n = Inf,
  lazy = FALSE
)

Value

A tibble with columns:

gvkey

Compustat company identifier

permno

CRSP permanent security identifier

linkdt

Start date of the link

linkenddt

End date of the link (missing values replaced with max date)

linktype

Type of link

linkprim

Link primacy

Arguments

wrds

A DBIConnection object returned by wrds_connect().

linktype

Character vector. Types of links to include. Defaults to c("LC", "LU", "LS"):

• "LC": Link confirmed by Compustat

• "LU": Link unconfirmed (valid but less certain)

• "LS": Link valid for secondary securities

linkprim

Character vector. Link primacy filters. Defaults to c("P", "C"):

• "P": Primary link identified by Compustat

• "C": Primary link identified by CRSP

n

Maximum number of rows to return. Defaults to Inf (all rows). Use a smaller value (e.g., n = 100) to preview data before downloading the full table.

lazy

If TRUE, returns a lazy tbl instead of collecting. Defaults to FALSE.

Details

The linking table comes from crsp.ccmxpf_lnkhist. Missing linkenddt values indicate ongoing links and are replaced with the maximum date in the table for easier date-range joins.

To use the link, join on gvkey and ensure your observation date falls within the linkdt to linkenddt range.

References

Ian Gow, Financial Accounting Research, Chapter on Identifiers: https://iangow.github.io/far_book/identifiers.html

See Also

get_compustat()

Examples

if (FALSE) {
wrds <- wrds_connect()
ccm <- link_ccm(wrds)

# Join with Compustat data
compustat <- get_compustat(wrds)
compustat |>
  dplyr::inner_join(ccm, by = dplyr::join_by(gvkey)) |>
  dplyr::filter(datadate >= linkdt, datadate <= linkenddt)

wrds_disconnect(wrds)
}