Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.

# Re: Re: st: Question on estimation procedure

 From Elena Quercioli To statalist@hsphsun2.harvard.edu Subject Re: Re: st: Question on estimation procedure Date Tue, 13 Nov 2012 11:56:26 -0500

```Hello,

My question was meant to get at STATA (estimation) capabilities and
not identifiability; here, in essence, is what I want to know. I want
to simultaneously estimate the common base and other coefficients of
this geometric function:

Y = c_0 + c_1[X_1+a^d2 X_2 + a^d3 X_3]

any ideas?

Elena Quercioli,
Economics Dept.,
CMU

On Mon, Nov 12, 2012 at 9:15 PM, Christopher Baum <kit.baum@bc.edu> wrote:
>
> <>
>
> Elena said
>
> Oops, my bad. I omitted to state that d1=0.
>
> Would you have any suggestions on how to estimate the non-linear model
> I illustrated?
>
>
>
> No, the model
>  Y = c_0 + c_1  X1 + c_2 a^d2 X2
> is still underidentified, even with the restriction that removes the alpha^0 term. Consider
>
> sysuse auto, clear
>
> forv c2 = 0.75(0.05)1.2 {
>         nl (price = {c0} + {c1} * mpg + `c2' * {alpha}^2 * weight)
>         nlcom `c2' * ([alpha]_cons )^2
> }
>
> As you can see, there is a locus of c2 and alpha values that render the same product (c2 * alpha^2),
> so the data cannot identify c0, c1, c2, alpha from three data vectors: iota, mpg, weight.
>
> Kit
>
> Kit Baum   |   Boston College Economics & DIW Berlin   |   http://ideas.repec.org/e/pba1.html
>                              An Introduction to Stata Programming  |   http://www.stata-press.com/books/isp.html
>   An Introduction to Modern Econometrics Using Stata  |   http://www.stata-press.com/books/imeus.html
>
>
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/faqs/resources/statalist-faq/
> *   http://www.ats.ucla.edu/stat/stata/
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/
```