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Re: st: pweight + aweight, double weights
Steve Samuels <email@example.com>
Re: st: pweight + aweight, double weights
Wed, 4 Aug 2010 17:14:05 -0400
I can see that the program is a little cryptic. To clarify:
I applied- svy: ratio- to R = length_2/length_1 and got asymmetric
confidence intervals for R by computing them on the log scale and
The rate that Jochen asked for is rate = (length_2 -
length_1)/length_1 = R - 1, and that is what the -antilog-- program
reports. "relc" meant "relative change", which seemed clear to me, at
On Wed, Aug 4, 2010 at 1:37 PM, Steve Samuels <firstname.lastname@example.org> wrote:
> If you do a probability weighted mean of the individual growth rates
> for a time period (single year, first year to last year) and weight by
> w = (initial value) x (probability weight), you would wind up with
> the rate based on the probability-weighted aggregated sums. So Stas's
> solution is exactly the solution you seek. Moreover, Stas's version
> will provide the correct standard error, one appropriate for a ratio
> You could also calculate the ratio estimate directly and get
> asymmetric CI's, which are likely to be more accurate than the
> symmetric intervals
> **************************CODE BEGINS**************************
> capture program drop _all
> program antilog
> local lparm el(r(b),1,1)
> local se sqrt(el(r(V),1,1))
> local bound invttail(e(df_r),.025)*`se'
> local parm exp(`lparm')
> local ll exp(`lparm' - `bound')
> local ul exp( `lparm' + `bound')
> di "relc = " 100*( `parm'-1) " ll = " 100*(`ll'-1) " ul = "
> sysuse auto, clear
> gen length_2 = displacement
> rename length length_1
> svyset _n
> svy: ratio length_2/length_1
> nlcom log(_b[_ratio_1])
> ***************************CODE ENDS***************************
> Steven Samuels
> 18 Cantine's Island
> Saugerties NY 12477
> Voice: 845-246-0774
> Fax: 206-202-4783
> On Wed, Aug 4, 2010 at 11:43 AM, Stas Kolenikov <email@example.com> wrote:
>> Who knows. You might be able to get identical answers, but you'll
>> spend more time trying to figure out the appropriate composition of
>> weights trying to reproduce the answer from those -total- commands.
>> On Wed, Aug 4, 2010 at 2:58 AM, Jochen Späth <firstname.lastname@example.org> wrote:
>>> Hello Stas,
>>> thank you very much for your advice. I'm aware of the possibility of calculating the aggregate sums of investment for different subpopoluations using the pweight and calculating the aggregate (=aweighted) growth rates from the newly-generated data. I was just wondering whether there were a more "flexible" approach, such as, say multiplicating the two weight variables and use the result in a single -tabstat- or something like that.
> On Tue, Aug 3, 2010 at 12:30 PM, Stas Kolenikov <email@example.com> wrote:
>> You would probably want to
>> svyset PSU [pw=your weight], strata(strata)
>> svy : total investment, over( year sector )
>> nlcom ([investment]_subpop_2 - [investment]_subpop_1)/[investment]_subpop_1
>> or whatever labels the -total- command is going to give to individual
>> On Tue, Aug 3, 2010 at 8:29 AM, Jochen Späth <firstname.lastname@example.org> wrote:
>>> Dear Statalisters,
>>> I have a question about weights, especially about "double weights".
>>> I have micro-data on firms containing information about their investment behaviour (amounts) for several years. I then went on to calculate the firms' individual (discrete) growth rates of investment, i.e.
>>> rate_t = (inv_t - inv_t-1) / inv_t-1
>>> and wish to use these individual growth rates to calculate average growth rates for, say, economic sectors. Thereby, I'd like to attach an aweight to the -tabstat-, -table- or other suitable command, such that firms with higher investments in t-1 contribute a higher share to the average growth rate. This is, of course, straightforward in Stata.
>>> However, since I have sampled data I need to attach to this operation also a pweight to get information for the population instead of the sample.
>>> Can I calculate the average growth rates from the individual ones or do I need to -collapse- or -table, replace- my data? It seems that -svyset- could be what I am looking for, but it seems rather complicated. Is there a way to avoid the -svyset- command and to go on with simple -tabstat- or alike instead?
18 Cantine's Island
Saugerties NY 12477
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