I have a question about "origin" and "enter" in stset using Stata 8.0. I am studing firms and their expansion into foreign markets. The firms are under observation from Jan 1 1991 to Dec 31, 2000. However, they are at risk of foreign expansion from their inception (when the firm was founded). I set up the data using the following command
stset edate, id(unique) failure(enter) enter(time entdate) origin(time foundy2) exit(time .)
Origin is the variable foundy2 which is an integer of the firm's founding date.
Enter is a variable that records the date Jan 1, 1991 for every observation, because this is the date when the firms became under observation. I believe that this is the correct syntax. However for some reason when I check the _t0 and _t dates and when I use stdes, the firms are not calculated as being at risk from their founding date. In fact some of the firms were founded in 1848 so their time at risk should be much higher.
Below is an example of the output from stedes. Note the earliest time at risk is 3403 and the max is 3653. Can anybody possibly help me with this. I would appreciate any help.
failure _d: enter
analysis time _t: (edate-origin)
origin: time foundy2
enter on or after: time entdate
exit on or before: time .
id: unique
|-------------- per subject --------------|
Category total mean min median max
------------------------------------------------------------------------------
no. of subjects 2060
no. of records 20671 10.03447 10 10 19
(first) entry time 17297.77 1096 16071 52595
(final) exit time 20950.77 4749 19724 56248
subjects with gap 1
time on gap if gap 250 250 250 250 250
time at risk 7524930 3652.879 3403 3653 3653
failures 71 .034466 0 0 9
------------------------------------------------------------------------------
Thanks,
Doug Thomas
Anderson Schools of Management
University of New Mexico
MSC05 3090
1924 Las Lomas NE
Albuquerque NM 87131-0001
Phone: (505) 277-8892
Fax: (505) 277-7108
[email protected]
http://www.unm.edu/~thomasd
Thanks,
Doug Thomas
Anderson Schools of Management
University of New Mexico
MSC05 3090
1924 Las Lomas NE
Albuquerque NM 87131-0001
Phone: (505) 277-8892
Fax: (505) 277-7108
[email protected]
http://www.unm.edu/~thomasd
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