Dear Claudio,
I ran into a similar question earlier this year. I was helped by
people on this list. Here is the link to the post.
http://www.stata.com/statalist/archive/2008-03/msg01106.html
Best,
Jeremy
On Tue, May 20, 2008 at 12:13 PM, Davide Cantoni
<[email protected]> wrote:
> Hello Claudio,
>
> this is the trick I use when I want to balance a panel (y is the
> outcome variable):
>
> *** begin code
>
> sort id year
> by id: egen nonmissing1to7 = count(y) if (year==1 | year==2 | year==3
> | year==4 | year==5 | year==6 | year==7)
> keep if nonmissing1to7==7
>
> *** end code
>
> Maybe there are more elegant solution around, but this one always
> works fine for me.
>
> Best
>
> Davide
>
>
>
> 2008/5/20 Claudio Cruz Cazares <[email protected]>:
>> Dear all!,
>>
>> I`m working in my Phd. dissertation but a have not find a solution for a crucial problem, hope you could help me.
>>
>> I have an unbalanced panel data of 4050 firms in 16 years but I have monotone and intermittent (since I clean the data from missing values of my dependent variables) missingness and as far as I know, the intermittent missingnes could cause problems when estimating fist differences.
>>
>> I wonder if someone could tell me how could I clean the sample. The easiest thing would be to balance it, but even I can see, after xtdes command, how many firms are in all periods, I can not find de way to keep just them. Is there any way to select the firms based upon their pattern?
>> Other solution is to eliminate the intermittent observations and keep those who died during the panel and those who growth within the panel, but how can I do that?
>>
>> I have generated a new variable in order to identify the missingness of a firm in a year.
>>
>> quietly by Identi: gen dy=year-year[_n-1]
>>
>> dy would be = 1 if there are non missing observation of the firm. Then, I drop the firms with a dy > 1. But I still have intermittent missigness!
>>
>> xtdes
>>
>> Freq. Percent Cum. | Pattern
>> ---------------------------+-----------------
>> 577 18.89 18.89 | 111111111111111
>> 158 5.17 24.06 | 11 . . . . . . . . . . . . .
>> 150 4.91 28.97 | 1 . . . . . . 11111111
>> 136 4.45 33.42 | . . . . . . . . . . 11111
>> 131 4.29 37.71 | 111111111111 . . .
>> 126 4.12 41.83 | 1 . . . . . . . . . . . . . .
>> 126 4.12 45.96 | 1111 . . . . 111 . . . .
>> 116 3.80 49.75 | 111 . . . . . . . . . . . .
>> 88 2.88 52.64 | 111111 . . . . . . . 11
>> 1447 47.36 100.00 | (other patterns)
>> ---------------------------+-----------------
>> 3055 100.00 | XXXXXXXXXXXXXXX
>>
>>
>>
>>
>> Thanks in advance
>>
>> Claudio
>>
>>
>> *
>> * For searches and help try:
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>> * http://www.stata.com/support/statalist/faq
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>>
> *
> * For searches and help try:
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> * http://www.ats.ucla.edu/stat/stata/
>
*
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