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st: Unbalanced Panel?

From   "Donald L. Alexander" <>
Subject   st: Unbalanced Panel?
Date   Mon, 25 Aug 2003 15:43:50 -0400

My colleague and I have been working with a data set that we believe is an 
unbalanced panel, but we are not certain. Let me describe it and then ask how I 
would use xtreg to estimate a regression model using these data.

The cross section consists of golfers which we observe over the time period 1992-
2001. We observe some of the golfers for 1 year, some for 2 (which may or may not 
be consecutive), some for 3 years, and so on. There are only 39 golfers that we 
observe for the entire time period (10 years). Some of the golfers that we observe in 
the early years leave and are replaced by new golfers. The golfers that leave are 
generally those that fail to make the cut (minimum money earnings) or those that 
choose to move to some other tour. The total number of golfers is 370 and the total 
number of observations is 1718.

Based on the discussion in Wooldridge, I think we satisfy the attrition criterion, which 
states that the decision to drop a golfer is related to the earnings variable (the 
dependent variable in our analysis). That is, a golfer is eliminated when he fails to 
make the earnings cut.

How should we handle this in Stata?

Don Alexander

Donald L. Alexander, Ph.D.
Department of Economics
Western Michigan University
1903 W. Michigan Avenue 
Kalamazoo, MI 49008-5330
Voice: 269-387-5526
Fax: 269-387-5637
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