Stata: Data Analysis and Statistical Software

So I cannot construct these pairs because for a particular time, t,
the rate exists in one location, but the rate in another location
starts after t or ends before t.

So the main thing I need to define is what I want done when data has
not yet started or is already finished in another country. I do not
know actually what the best solution is. This is my main question.
I found something about extrapolation (if this is to be the solution)
but I learn that extrapolation usually has quite a wide margin of
error!! Apart from that, I have no idea how to implement it in Stata.

Do you think that it would be better to try and create a more
symmetric sample so as the start and end dates across countries to be
very similar?
It is a data analysis problem. I need some help....

Joales
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