I am merging two datasets:
1) One which includes Reuters US companies' RICs and the number of news linked to each company;
2) Compustat US, taking data from 1996 to 2018.
I have few questions:
In order to merge them, I consider that Reuters RICs without the stock exchange (e.g. AAPL for Apple) correspond to Compustat Company Ticker, is this correct? Looking through the Reuters RICs of companies mentioned in news during 2019, I found three exceptions to this rule, one of them is Moog Inc, whose Reuters' RIC is MOOGa, while Compustat Ticker is MOOG.A. The other two cases are different in the same way (JWa - JW.A and BRKb - BRK.B). I would like to know whether this is actually true.
Do the Reuters RICs change over time? Are they re-used or are they uniquely assigned to firms from 1996? For example, if I find a company's RIC in 1996, is it sure that this RIC will be always attached to the same company and will not be assigned to another company in the following years? In case RICs actually change, is there a guide with all the changes (possibly a guide that does not require to login in any website)?