Hello everyone,
Based on my title post it seems the question is repeated but no it’s different.
my question is:
I have dataset file consists of a number of independent directors variable. I have created a dummy variable coded 1 if there is at least one independent director on the committee.
I need to remove the firms that have no independent directors on the committee. Maybe it seems to be easy by dropping the observations== 0 ( using either the dummy variable or the variable of number of independent directors). But, I Need to remove those firms with no independent directors over the study period (2000-2006). This means that the remaining observations should consist of a firm that ( for example) did have no independent in the year 2000 then it appointed independent directors in 2001 or 2002.
Because I want to compare between the firm performance before appointing independent directors and after.
kindly who can help me out to do this and create dummy variable coded 1 after appointing independent directors zero before.

please please help.
thank you in advance