st: Random Sample Selection in Panel Data

[Dennis Kramer <dkramerii@gmail.com>]

I have a large panel data sets (4 years-- 250,000 + records per year)
and I want to generate four random sample groups to test the stability
of the estimates. However, I want to ensure that if a ID is selected
in Year 1 then are are subsequently selected into the sample random
sample for Years 2, 3, and 4.

I know for a cross-sectional random sampling the code is as follows:

generate rannum = uniform()
egen grp2 = cut(rannum), group(4)

Does anyone have any insight into modifying the above syntax to
automatically include years2, 3, 4, ids in the same sample as the
selected Year 1 ID??

Thank you
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