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Re: st: XTFRONTIER: How to interpret Total Efficiency Measures
From
Scott Merryman <[email protected]>
To
[email protected]
Subject
Re: st: XTFRONTIER: How to interpret Total Efficiency Measures
Date
Tue, 13 Apr 2010 11:27:05 -0500
On Mon, Apr 5, 2010 at 11:09 AM, Victor Waters <[email protected]> wrote:
> Dear StataListers,
>
> I am a little confused about the magnitude of the total efficiency
> measure. My XTFRONTIER with time varying decay model,
> runs well, almost all of the coefficients are as expected.,
>
> My total efficiency measures (for all units) are very low - between .1
> and .25. What importance should I attach to this?
> Does it mean all of the units are very inefficient?
Or the model is misspecified.
<snip>
> If eta is not 0, can I compare ti and tvd efficiency measures?
There is a significance test for eta to distinguish between the two models.
In the example below, the tvd model has efficiency estimates on that
are very low - the average less than 0.003 while the average
efficiency estimates for the ti model is about 0.50. However, one a
time trend is added to the model (capturing technological progress),
the efficiency estimates are similar.
. webuse grunfeld,clear
. gen lninvest = ln(invest)
. gen lnmval = ln(mval)
.
. qui xtfrontier lninvest lnmval, ti nolog
. predict te_ti, te
.
. qui xtfrontier lninvest lnmval , tvd nolog
. predict te_tvd, te
.
. sum te*
Variable | Obs Mean Std. Dev. Min Max
-------------+--------------------------------------------------------
te_ti | 200 .490895 .2736979 .1121026 .9170025
te_tvd | 200 .0027195 .0019911 .0001452 .0087726
.
. qui xtfrontier lninvest lnmval time, ti nolog
. predict te2_ti, te
.
. qui xtfrontier lninvest lnmval time, tvd nolog
. predict te2_tvd, te
.
. sum te2*
Variable | Obs Mean Std. Dev. Min Max
-------------+--------------------------------------------------------
te2_ti | 200 .3899374 .2795348 .0356406 .9245906
te2_tvd | 200 .4083181 .2734767 .0326259 .9357629
Scott
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