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# Re: st: loops for regions

 From Chiara Mussida To statalist@hsphsun2.harvard.edu Subject Re: st: loops for regions Date Wed, 5 Sep 2012 22:52:35 +0200

```tried to write my own file since the next step will be, as i hope, to
compute a Lilien index for each region. I tried to search for a stata
program but i did not succeed. Does anybody know whether it exists?
Thanks

On 05/09/2012, Nick Cox <njcoxstata@gmail.com> wrote:
> The first line confuses the -if- command and the -if- qualifier.
>
> I didn't look in detail at later code, as there should be no need to
> write your own code, as many programs exist. -search inequality- for a
>
> In fact, in many ways this is a calculator problem easily tackled with
> Mata.
>
> . mata
> : freq = (0, 0, 3, 9, 9)
> : pr = freq :/ sum(freq)
> : sum(pr:^2)
>   .387755102
>
> In fact, zero frequencies map to zero squared proportions and can be
> omitted.
>
> This index, although often attributed to Herfindahl by economists who
> know only their only literature, was in essence invented decades
> before by Gini. I don't have the reference in my head, but I think it
> is in Bishop, Y., Fienberg, S.E. and Holland, P.W. 1975. Discrete
> multivariate analysis. Cambridge, MA: MIT Press. Please trump me by
> providing a yet earlier reference.
>
> Nick
>
> On Wed, Sep 5, 2012 at 5:15 PM, Chiara Mussida <cmussida@gmail.com> wrote:
>
>> I want to generate a variable herf1 which takes the value of the below
>> index for region 1, and thereafter repeat this loop for all the region
>> in my dataset. The problem is that with the below command I get the
>> herf1 index for region 1, which is identycal in value (I tried) to the
>> herf2 for region2 whether I repeat this llop for region2, by starting
>> with "if reg==2, and so forward for all the regions.
>>
>> if reg==1 {
>> tab cat12_2, gen(categ)
>> forvalues k = 1 2 to 12 {
>> sum categ`k', meanonly
>>         gen share`k'=r(mean) if reg==1 /*shares of each occ cat on the
>> total
>> occupation, time t*/
>> }
>> }
>>
>> gen herf1=(share1)^2 + (share2)^2 + (share3)^2 + (share4)^2 +
>> (share5)^2 + (share6)^2 + (share7)^2 + (share8)^2 ///
>> + (share9)^2 + (share10)^2 + (share11)^2 + (share12)^2  /*Herfindhal
>> Index Region1*/
>> the variable reg takes 1 for region1, 2 for region2...up to 20 for
>> region20. In other words, Stata does not compute the specific index
>> for each region, but the same index region by region.
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>

--
Chiara Mussida
PhD candidate
Doctoral school of Economic Policy
Catholic University, Piacenza (Italy)
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```