For historical analysis on securities, researchers use permanent identifiers, such as PERMNO, PERMCO, and GVKEY that never change for the duration of the company’s life span regardless of the name changes or other instances and are never being reused.
PERMCO and PERMNO are unique permanent identification numbers assigned by CRSP to all companies listed in CRSP dataset.
- PERMCO is a unique company level identifier that remains unchanged throughout the whole term of company’s existence even if the company changed name/s.
For example, the PERMCO 21566 stays unchanged through the whole history of the company that started with the name Consolidated Grocers Corp. in 1946, then changes to Consolidated Foods Corp.(CFD) in 1954, then became Sara Lee (SLE) in 1985, and as of 2012 is called Hillshire Brands Co. (HSH).
- PERMNO is a unique stock (share class) level identifier. While most of the companies have one class shares, some companies have more than one class shares traded at different prices, and this is the reason why a company can have more than one PERMNOs.
For example, CBS Corporation (CBS) has two classes of shares (at the time of publishing of this document), and respectively two PERMNOs. On December 24, 2018 the closing price of shares with PERMNO 75104 was $42.440 and shares with PERMNO 76226 closed at $42.020.
GVKEY (Global Company Key) is a unique number assigned to each company in the Compustat-Capital IQ database.
