st: Calculating returns if a stock is delisted

["C. Evans" <ce306@cam.ac.uk>]

Dear Statalist

My dataset goes from 1964 to 31 December 1997. I am looking at stock 
returns and trying to create a new variable that will be related to 
returns. This new variable will use DelistRet (delisted return) if avilable 
and then use the delist code to determine what to multiply it by. As such, 
a delist code of between 500 and 600 would be multiplied by -0.3. However, 
sometimes the stock finishes at q date before 31 December 1997 and has no 
delistcode or delistret, for this I need to multiply the Return by -1. For 
all the other days when the stock is trading and not delisted I would just 
use Return.

Below is an example of my data (not going all the way to 31Dec1997) 

Id  Date   DelistCode DelistRet Return Day Month   Year
1  2Jan1964    .        .        1.1    2    1     1964 
1  3Jan1964   520       -0.7     1.2    3    1     1964
2  2Jan1964    .        .        1.2    2    1     1964
2  3Jan1964    .        .        1.4    3    1     1964
2  4Jan1964    .        .        1.3    4    1     1964

I was trying to do this in stages as my stata skills are not great. I had 
an idea to use:

egen delisted = 1 if max(date)  != day==31 & month==12 & year ==1997

Which I thought would give a value of 1 for the stocks that didn't reach 
the max date. I'd be much happier to use a different line of code and I am 
open to any suggestions.

Best Regards,
Chris Evans 

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