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RE: st: number of missing from previous year
The word "missing" is heavy with connotations.
1. An observation can have a value for a given
variable that is missing, meaning numeric missing
or string missing "" depending on the variable.
2. Something can be omitted from, or not present
in, a dataset.
What you want is neither of these.
As I understand it, you want to count the people
who left each firm in any given year.
One logic is that if someone left a firm in
a given year, then that was their last year
with the firm.
Hence you can tag leavings with
bysort firm personid (year): gen left = _n == _N
except that you would not count someone as
leaving who is still there in the last year
bysort firm year : replace left = 0 if year == year[_N]
Now you can count how many left each firm in
by firm year: egen number_left = total(left)
tabdisp firm year, c(number_left)
If you prefer to associate leavings with the next year,
gen nextyear = year + 1
tabdisp firm nextyear, c(number_left)
I don't know what you want to do about anybody
who left a firm and then came back to the same
firm within the period of study.
> Thanks for the prompt help. My mistake to imply I only have 2
> years data but
> actually I have 8 years. I think the change should be for 1994 because
> that's when the change occurs. In addition, this may be not
> what I want
> because the code counts number of people change from firm to
> firm. If a
> person retires and never appears in the data, then she is not
> counted in the
> code I think, but should be. Again, I need to count the
> missing persons from
> year to year. Could you help again?
> bysort firm personid: gen count=_N if year==1993 | year==1994
> * Count would equal to 2 if a person is with the same firm for both
> 1993 and 1994, 1 if this person was only with this firm in 1993 or in
> bysort firm year: egen changed=total(count) if count==1 & year==1993
> variable changed would contain the number of employees who were with
> this firm in 1993, but no longer remain employed with the same
> employer in 1994. it'd be all missing values for this variable in
> > I have panel dataset, which has firm ID, year, and person ID for the
> > working in the firm. I want to calculate the number of
> staff changes for
> > same company for each year. For example, the data is as follows.
> > FIRM YEAR PERSONID
> > 1 1993 2
> > 1 1993 4
> > 1 1993 276
> > 1 1993 23456
> > 1 1993 853
> > 1 1994 2
> > 1 1994 276
> > 1 1994 853
> > 1 1994 3452
> > 1 1994 224
> > I already sort firm and year. As you can see, the change of
> staff for firm
> > in 1994 should be 2 because only person 2, 276 and 853 are
> retained. I
> > want to count how many persons are missing from previous year.
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