Re: st: how to creating a variable recording the sum of another variable by group in panel data?

["natalie chan" <natalie.channew@googlemail.com>]

I have also tried to create an identifier using this:

egen id=group(year, industry)

but Stata generates an error message saying "invalid syntax". I can't
found out what's wrong with this. Any help will be appreciated.

Thanks again.

On 5/20/07, natalie chan <natalie.channew@googlemail.com> wrote:
> Dear statalister,
>
> I have a problem in creating a variable recording the sum of another
> variable by group in panel data. I would be grateful if any of you
> could help me in this.
>
> The data is a 12 year unbalanced panel, including more than 15000
> domestic firms and 9000 foreign firms in 82 three-digit industries. I
> want to calculate the foreign presence in each three-digit industry,
> that is,
>
> FDI= sum of the output of foreign firms/sum of the output of all
> firms, for each industry and each year.
>
> I tried this:
>
> (*first, calculate the sum of output of all firms in each industry)
> egen alloutput=total(output) if year==1986, by(industry)
> egen alloutput87=total(output) if year==1987, by(industry)
> ......
> egen alloutput97=total(output) if year==1997, by(industry)
>
> replace alloutput=alloutput87 if year==1987
> ...
> replace alloutput=alloutput97 if year==1997
>
>  (*second, calculate the sum of output of foreign firms in each industry)
> egen FDI=total(output) if year==1986 & firm=="foreign", by(industry)
> egen FDI87=total(output) if year==1987 &firm=="foreign",  by(industry)
> ......
> egen FDI97=total(output) if year==1997, & firm=="foreign", by(industry)
>
> replace FDI=FDI87 if year==1987 & firm=="foreign"
> ...
> replace FDI=FDI97 if year==1997 & firm=="foreign"
>
> egen FDInew=max(FDI), by(industry)
> egen FDInew87=max(FDI) if year==1987, by(industry)
> ....
> egen FDInew=max(FDI) if year==1997, by(industry)
>
> replace FDInew=FDInew87 if year==1987
> ...
> replace FDInew=FDInew97 if year==1997
>
> (*third,calculate the foreign presence)
> gen FDIpresence=FDInew/alloutput
>
>
> However, some of the ratio are over 1, which is not possible. I tried
> to use "in" instead of "if" in the above syntax and obtained different
> results.
>
> I know I must have made some mistakes but can't figured it out myself.
> Could anyone here help me? Thanks a lot.
>
> Natalie.
> *
> *   For searches and help try:
> *   http://www.stata.com/support/faqs/res/findit.html
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/