Firm Age from CRSP

[Helen Chang]

Hi,

I would like to get data of the first year when the firm appears in CRSP. Then merge this dataset with the panel data from Compustat. Anyone knows where I can get the data from WRDS/CRSP specifically and how to complete the merge? I used the date from CRSP Events--Names, is it the right one for my purpose?

Thank you for your help in advance!

[Devra Golbe]

Hi Helen,

It may be helpful to think of CRSP as a listing of securities, rather than firms. Each security is identified by a PERMNO. Each firm is identified by a PERMCO. A company (PERMCO) can have more than one security (PERMNO) at any time. COMPUSTAT identifies firms by GVKEY. The easiest way to link them is using the CRSP/COMPUSTAT Merged (CCM) database on WRDS. If that is not available to you, you can merge by CUSIP. There are help files and sample programs on the WRDS site.

Best,
Devra

[Helen Chang]

I don't have CCM database, thus I make the cusip from COMPUSTAT into a 8-digit number, since CRSP has 8-digit cusip number. These two datasets were merged successfully, but I don't know whether this method will cause some potential problems...

[Devra Golbe]

This page from Rui Dai (http://www.ruidaiwrds.info/data/link...-and-compustat) describes the issues arising from a merge based on CUSIP.

[David Benson]

Compustat has a field called IPODATE which is the date of a company's initial public stock offering. As Compustat states, "if the date of a company's initial public stock offering is not available, the first trading date in the major exchange is used." Once you have that it's easy in Stata to extract the year of the IPO (which would tell you the year it appears in CRSP).

I know you are looking to calculate Firm_age yourself within Stata (which is easy enough once you get the data merged as you mention), I would also just note that Jay Ritter at the Univ of Florida has "Founding dates for 10,266 firms going public in the U.S. during 1975-2015" as an Excel file available for download on his website here


David Benson
Dept. of Management
Brigham Young University

[Helen Chang]

Thank you for your help, David!

[Shashi Kant]

The updated link of Firm age data by the kind Jay Ritter is here: https://site.warrington.ufl.edu/ritt...ding-dates.pdf
Excel sheet link is available in the document.