Hi there!
I have a panel dataset taken from the Mexican Population Census where the observations are localities (unique_id) observed every five years (variable year, taking values 1990, 1995, 2000...). It is a balanced dataset as it is.
What I want to do is to interpolate all of these variables - filling in the values between each census year for every locality. My desired end result is a panel of my localities where the localities are observed yearly, rather than every five years (and the values for the four years in between are created using ipolate).
However, my understanding is that usually ipolate is applied to panel datasets where all the yearly observations are already present (but with missing values) and the job is about filling them in (rather than creating them anew!). In my case, the problem is in fact that I'd somehow have to "copy" observations before filling them in. Is there a straightforward way to do this?

Just to make this more concrete, my current dataset is like this:
unique_id year variable
1 1990 2
1 1995 12
1 2000 22
1 2005 32
1 2010 42
2 1990 52
2 1995 62
And the desired dataset would be something like:
unique_id year variable
1 1990 2
1 1991 4
1 1992 6
1 1993 8
1 1994 10
1 1995 12
1 1996 14
1 1997 16
1 1998 18
(etc) Where in bold are the observations that are retained from the original dataset.


I do hope this is clear, but do not hesitate to let me know if it isn't.
Thank you all for your help!