I have a data set with around 90,000 observations and I am merging it with
another dataset with around 3 million observations. However, when I merge the
two, the number of '3s' in the _merge variable exceeds the 90,000 in the master
file by a few thousand, indicating that there is more than one observation in
the using file for some of the observations in the working file.
Does anyone know if it is possible to prevent Stata from picking up the
additional observations from the using file (i.e., constraining the observations
merged to the 90,000 in the working file)?
Many thanks in advance
Mark Clatworthy
Cardiff University
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