Ada,
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?
Wanli
-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Ada Ma
Sent: Sunday, August 13, 2006 5:12 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: number of missing from previous year
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
1994.
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
1994.
On 8/13/06, Wanli Zhao <zhaowl@temple.edu> wrote:
> Guys, please help me with a data management question. I spent a day and
> cannot figure out.
> I have panel dataset, which has firm ID, year, and person ID for the
people
> working in the firm. I want to calculate the number of staff changes for
the
> 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
1
> in 1994 should be 2 because only person 2, 276 and 853 are retained. I
only
> want to count how many persons are missing from previous year. I
appreciate
> your kind help.
>
> Wanli
>
> *
> * For searches and help try:
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> * http://www.stata.com/support/statalist/faq
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>
--
Ada Ma
Research Fellow
Health Economics Research Unit
University of Aberdeen, UK.
http://www.abdn.ac.uk/heru/
Tel: +44 (0) 1224 553863
Fax: +44 (0) 1224 550926
*
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*
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