[Limdep Nlogit List] Help with Error 805
Zhi Shen
Z.Shen at lboro.ac.uk
Sat Oct 13 08:14:04 EST 2007
Deal all,
I am trying to model the Battese and Coelli (1992) time varying models using the cost function. I found the estimated parameters are almost the same as the estimated parameters in the Pooled cross sectional model with the half normal distribution assumption in the inefficiency term. The error message comes up with the results, saying
Warning 141: Iterations:current or start estimate of sigma is nonpositiv
Error 805: Initial iterations cannot improve function.Status=3
Can anyone explain what the problem is and are there any solutions to the problem?
I'm posting the results below.
============================================================================
--> fron;cost;lhs=c;rhs=translog,lnE;pds=ni;model=BC;eff=uibc $
Warning 141: Iterations:current or start estimate of sigma is nonpositiv
Maximum iterations reached. Exit iterations with status=1.
+---------------------------------------------+
| Limited Dependent Variable Model - FRONTIER |
| Maximum Likelihood Estimates |
| Model estimated: Oct 12, 2007 at 11:09:57PM.|
| Dependent variable C |
| Weighting variable None |
| Number of observations 2155 |
| Iterations completed 51 |
| Log likelihood function 123.9024 |
| Number of parameters 31 |
| Info. Criterion: AIC = -.08622 |
| Finite Sample: AIC = -.08579 |
| Info. Criterion: BIC = -.00458 |
| Info. Criterion:HQIC = -.05636 |
| Variances: Sigma-squared(v)= .01561 |
| Sigma-squared(u)= .11401 |
| Sigma(v) = .12495 |
| Sigma(u) = .33765 |
| Sigma = Sqr[(s^2(u)+s^2(v)]= .36002 |
| Stochastic Cost Frontier, e=v+u. |
+---------------------------------------------+
+--------+--------------+----------------+--------+--------+----------+
|Variable| Coefficient | Standard Error |b/St.Er.|P[|Z|>z]| Mean of X|
+--------+--------------+----------------+--------+--------+----------+
---------+Primary Index Equation for Model
Constant| 1.48011477 .15406438 9.607 .0000
Y1 | .04912134 .04390773 1.119 .2633 8.22688477
Y2 | .15902832 .03816858 4.166 .0000 7.87854052
Y3 | .10837206 .03232890 3.352 .0008 4.14496927
Y4 | .42060086 .07977893 5.272 .0000 8.78307806
W1 | .62125222 .03530205 17.598 .0000 -3.02090271
W2 | .25964963 .03530003 7.356 .0000 -3.08089278
Y11 | -.01081874 .00774773 -1.396 .1626 36.1459176
Y12 | .12748994 .01502006 8.488 .0000 68.6268632
Y13 | .01805905 .00744020 2.427 .0152 37.3624414
Y14 | -.13090313 .01416448 -9.242 .0000 76.3470559
Y22 | -.02752224 .00535760 -5.137 .0000 33.2158971
Y23 | .02943329 .00568884 5.174 .0000 35.9359113
Y24 | -.13698355 .01610101 -8.508 .0000 73.0650319
Y33 | .03213044 .00543019 5.917 .0000 10.4248555
Y34 | -.07450431 .01136528 -6.555 .0000 39.6117654
Y44 | .36259586 .02767744 13.101 .0000 40.5621250
W11 | .00401270 .00790400 .508 .6117 5.27504492
W12 | -.02509200 .00775883 -3.234 .0012 10.2272303
W22 | .02241561 .00848613 2.641 .0083 5.52520057
Y1W1 | .00399844 .00719339 .556 .5783 -24.4287397
Y1W2 | .00287702 .00751943 .383 .7020 -24.3168234
Y2W1 | .02198172 .00752668 2.921 .0035 -23.3631088
Y2W2 | -.01184879 .00674389 -1.757 .0789 -23.4491970
Y3W1 | -.02585426 .00490485 -5.271 .0000 -12.0716052
Y3W2 | -.00026893 .00437656 -.061 .9510 -11.9938237
Y4W1 | .00372905 .01183016 .315 .7526 -26.0898590
Y4W2 | -.00890171 .01170410 -.761 .4469 -26.1046710
LNE | .03820777 .00978386 3.905 .0001 6.47488942
---------+Variance parameters for compound error
Lambda | 2.70230373 .14300880 18.896 .0000
Sigma | .36002465 .00013751 2618.240 .0000
Initial iterations cannot improve function.Status=3
Error 805: Initial iterations cannot improve function.Status=3
Function= -.18176915671D+02, at entry, .16413602848D+02 at exit
+---------------------------------------------+
| Limited Dependent Variable Model - FRONTIER |
| Maximum Likelihood Estimates |
| Model estimated: Oct 12, 2007 at 11:09:57PM.|
| Dependent variable C |
| Weighting variable None |
| Number of observations 2155 |
| Iterations completed 1 |
| Log likelihood function 18.17692 |
| Number of parameters 32 |
| Info. Criterion: AIC = .01283 |
| Finite Sample: AIC = .01329 |
| Info. Criterion: BIC = .09711 |
| Info. Criterion:HQIC = .04366 |
+---------------------------------------------+
| Frontier model estimated with PANEL data. |
| Estimation based on 320 individuals. |
| Variances: Sigma-squared(v)= .01561 |
| Sigma-squared(u)= .11401 |
| Sigma(v) = .12495 |
| Sigma(u) = .33765 |
| Sigma = Sqr[(s^2(u)+s^2(v)]= .36002 |
| Stochastic Cost Frontier, e=v+u. |
| Time varying u(i,t)=exp[-eta(t-T)]*|U(i)| |
+---------------------------------------------+
+--------+--------------+----------------+--------+--------+----------+
|Variable| Coefficient | Standard Error |b/St.Er.|P[|Z|>z]| Mean of X|
+--------+--------------+----------------+--------+--------+----------+
---------+Primary Index Equation for Model
Constant| 1.48011477 .07113658 20.807 .0000
Y1 | .04912134 .02164988 2.269 .0233 8.22688477
Y2 | .15902832 .01830169 8.689 .0000 7.87854052
Y3 | .10837206 .01088971 9.952 .0000 4.14496927
Y4 | .42060086 .03619382 11.621 .0000 8.78307806
W1 | .62125222 .01235709 50.275 .0000 -3.02090271
W2 | .25964963 .01846957 14.058 .0000 -3.08089278
Y11 | -.01081874 .00413896 -2.614 .0090 36.1459176
Y12 | .12748994 .00665530 19.156 .0000 68.6268632
Y13 | .01805905 .00386344 4.674 .0000 37.3624414
Y14 | -.13090313 .00654388 -20.004 .0000 76.3470559
Y22 | -.02752224 .00190062 -14.481 .0000 33.2158971
Y23 | .02943329 .00255122 11.537 .0000 35.9359113
Y24 | -.13698355 .00620879 -22.063 .0000 73.0650319
Y33 | .03213044 .00171609 18.723 .0000 10.4248555
Y34 | -.07450431 .00495606 -15.033 .0000 39.6117654
Y44 | .36259586 .00986814 36.744 .0000 40.5621250
W11 | .00401270 .00200633 2.000 .0455 5.27504492
W12 | -.02509200 .00206129 -12.173 .0000 10.2272303
W22 | .02241561 .00303324 7.390 .0000 5.52520057
Y1W1 | .00399844 .00211051 1.895 .0582 -24.4287397
Y1W2 | .00287702 .00320399 .898 .3692 -24.3168234
Y2W1 | .02198172 .00290156 7.576 .0000 -23.3631088
Y2W2 | -.01184879 .00295487 -4.010 .0001 -23.4491970
Y3W1 | -.02585426 .00190452 -13.575 .0000 -12.0716052
Y3W2 | -.00026893 .00194141 -.139 .8898 -11.9938237
Y4W1 | .00372905 .00410056 .909 .3631 -26.0898590
Y4W2 | -.00890171 .00563595 -1.579 .1142 -26.1046710
LNE | .03820777 .00500994 7.626 .0000 6.47488942
---------+Variance parameters for compound error
Lambda | 2.70230373 .00595257 453.973 .0000
Sigma(u)| .33764737 .00076561 441.020 .0000
---------+Eta parameter for time varying inefficiency
Eta | .01000000 .00285833 3.499 .0005
Many thanks for the help.
Regards,
Zhi
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