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From |
Federico Belotti <f.belotti@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Different result of Technical Efficiency with Frontier 4.1 and Stata |

Date |
Tue, 1 Oct 2013 13:05:25 +0200 |

Vikash Vaibhav <vikashv@igidr.ac.in> found dramatically different results comparing Stata with Tim Coelli's Frontier 4.1. First, I would like to ask to Vikash which Stata command has been used for the estimation. Second, in my experience the two softwares give exactly the same results. I compared the user-written command -sfpanel- (from SSC) and FRONTIER 4.1 for the Battese and Coelli (1995) model using a simulated dataset that can be downloaded at http://www.econometrics.it/data/FRONTIER41vsSFPANEL.zip Data has been simulated from the following normal - truncated normal production model y_it = 1 + 0.3 x1_it + 0.7 x2_it - u_it + v_it where u_it is truncated normal with mean mu_it = 1 + 0.5 zmu_it and unit variance and v_it is normal with mean 0 and variance = 0.25. To run the estimation in Stata you can use the data file "simd-dta.dta" and the do file "check.do". To run FRONTIER 4.1 you can use the "dta.txt" and "ins.txt" files. I didn't find appreciable differences, considering also that the two log-likelihoods (the -sfpanel- and FRONTIER 4.1 ones) are differently parametrized. So, I'm wondering if you have some problems in variables and/or instruction file definition. On the other hand, I found appreciable differences using real data but only when the data has been transformed using, for instance, the log_var = log(var+0.1) trick to get rid of the log-zero problem. Usually this kind of tricks creates huge disproportions in the data which can be handled differently by the optimization engine of different software. A useful discussion on this issue can be found at http://stats.stackexchange.com/questions/30728/how-small-a-quantity-should-be-added-to-x-to-avoid-taking-the-log-of-zero Hope this helps, Federico References Battese, G., and T. Coelli. 1995. A model for technical ineciency effects in a stochastic frontier production function for panel data. Empirical Economics 20: 325-332. On Oct 1, 2013, at 7:22 AM, Vikash Vaibhav wrote: > This is with respect to the dramatically different result that i got when i > compared the results of technical efficiency estimated from Frontier 4.1 and > Stata. (two more student here has the same problem and with a different > dataset). I do not think that it could have been due to differing > algorithms or some other things that vary across statistical packages. > I would like to point out the following observations: > > 1. The results were different in case of cross section data. But they did > not differ a lot. > 2. The results for the panel data were hugely different with the two > software. > > I have used Stata IC version11.1 (for windows). > I have used Frontier 4.1 package freely available on CEPA website. > Any help ?? > > -- > Thanks & Regards, > Vikash vaibhav > * > * 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/ -- Federico Belotti, PhD Research Fellow Centre for Economics and International Studies University of Rome Tor Vergata tel/fax: +39 06 7259 5627 e-mail: federico.belotti@uniroma2.it web: http://www.econometrics.it * * 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/

**Follow-Ups**:**Re: st: Different result of Technical Efficiency with Frontier 4.1 and Stata***From:*Vikash Vaibhav <vikashv@igidr.ac.in>

**Re: st: Different result of Technical Efficiency with Frontier 4.1 and Stata***From:*Vikash Vaibhav <vikashv@igidr.ac.in>

**References**:**st: Different result of Technical Efficiency with Frontier 4.1 and Stata***From:*Vikash Vaibhav <vikashv@igidr.ac.in>

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