Yes, you are right. It is tried to start from 1 Jan 1980. However, if the stock is not available then, it will pick the first close where it is available.
Speaking of which, I cannot remember why I chose 1980 1 Jan. Maybe better to choose the first transaction date of user. What do you think?
My thought is that first transaction date of user will reflect a better comparison between the index vs portfolio. So for example, if the 1st transaction is on 20 Jan 2004, then the computation of the index will start from 20 Jan 2004 vs 1st transaction of the portfolio.
I don’t know whether there is any big difference in the computation. Anyone has any advise on this?