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st: Controlling for atrittion in panel, or creating a panel without atrittion


From   Laurie Molina <molinalaurie@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Controlling for atrittion in panel, or creating a panel without atrittion
Date   Wed, 22 Feb 2012 19:26:40 -0600

Dear all,
I have a database of 24 million observation, for 10 periods of time.
For each observation i have an id unique over time that allows me to
merge the 24 million observations in each of the 10 periods.
However i want to take a sample of the population because this very
large database is not easy to work with.

I seem to have two options:
1. To take a random sample at the first period and then merge the
databases to have a panel. In this case my panel will have attrition.
In fact by the last period the attrition rate (comparing period 1
observations with period 10 observations will be of almost 50%). The
remaining sample size much smaller than the original sample size is
leading to representativeness issues.
2. To take a random sample of the observations that appear on the
database in all the periods. If attrition is not random, then i would
have a population that is different to the original population, and
hence my random sample may not be representative for the original
population, but only for the population defined by all the
observations that appear in the database in all periods.

Which option do you think i should take?

Thank you very much in advance as always!
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