How do I merge ThomsonOne data to CRSP data in M&A analysis

[Bo Wang]

Hi everyone,

I am doing a Mergers and Acquisition analysis, and having difficulty to merge my ThomsonOne data with CRSP data. I want to add Announcement Date from ThomsonOne dataset to CRSP dataset so I could calculate CARs. However, since some acquirers take several acquisitions during the sample period and the acquirer permno are not unique, so I can't merge CRSP to ThomsonOne by using the acquirer company Permno. I understand I should construct some variables that is unique so I can use m:1 merge. I haven't figure out how to do that. Can someone please tell me how to do that?

Many thanks,
Bo

[Phil Bromiley]

You can merge m to m - see documentation. If you had unique Permno's for companies, you could do the merge. The problem is not uniqueness per se - it is getting the right merge. What exactly does it mean for a company to have multiple Permno's? If you look on WRDS, it has some information on merging CRSP and Compustat that might be helpful. How big is your sample? Could you fix the Permno's manually?

Generally, providing a sample of the data and desired outcome is helpful. See the FAQ.

[Bo Wang]

Hi Phil,

Thanks for your response. Sorry I wasn't very clear about my sample, but I have figured out how to do that.

Thanks,
Bo