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st: problem levpet command

From   pim de Nijs <>
To   <>
Subject   st: problem levpet command
Date   Thu, 11 Dec 2008 17:46:01 +0100


My knowledge about Stata is limited and a feel ashamed that i have to bother you with my question because maybe I just made a stupid mistake in the command that I use. But I really do not know how I can solve the problem and I could not find a solution on the internet. 

I want to use the following command:

. levpet logSales, free(logEmployees) proxy(logMaterials) capital(logCapital) i(number) t(Year) revenue 

I get the following error:

repeated time values within panel

I have no idea why i get the ''repeated time values within panel'' error. I am 100% sure that there are no duplicates:

. dupliactes list Year number

result: no observations are duplicates

By only using a part of my dataset i get an idea what the problem is:

. levpet logSales if (NACE<=1531), free(logEmployees) proxy(logMaterials) capital(logCapital) i(number) t(Year) revenue 

Now I get the results of the levpet command. However there is something strange:

Dependent variable represents revenue. Number of obs = 148
Group variable (i): number Number of groups = 5756
Time variable (t): Year
Obs per group: min = 1
avg = 4.1
max = 5

The number of observations is 148 and the number of groups is 5756? Then I see that the average number of observations per group is 4.1 This means that the number of groups should be 36 and not 5756.

I really have know idea what is going wrong. I just like to get the levpet results for my whole dataset. The . help levpet command do not give me the answer. Others papers that I have read and that are using the levpet command are telling that it is straightforward to use the levpet command. 

Can someone help me

Yours sincerely

Jouw nieuws en entertainment, vind je op!
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