st: Longitudinal sampling (many waves)

[Laurie Molina <molinalaurie@gmail.com>]

Hi guys,
I was wondering if stata has any command for longitudinal sampling.

I have a database which allows me to follow the same observations over
time. However, some of these observations dissapear over time, and
some new observations appear as well, as time goes by.
I would like to take a sample that is representative at every period
of time, that captures the attrition rate of the population, as well
as the rate of new observations entry.
Finally, i would like to be able to update this sample over time, that
is: if i have a sample that satisfies the above requirements from time
T to time T+10, in time T+11 i want to be able to take a new sample,
only on time T+11 observations, and add this new sample to the T to
T+10 sample database, and make sure that it still satisfies (taking in
to account the new T+11 observations), all the above requirements.

Do you think that it is possible to do such kind of sampling in Stata?

Thank you all very much!
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/