I can't speak for STATA. I will answer in terms of Stata.
Scientifically, doing this -- even interpolation rather than
extrapolation -- would seem difficult to
justify on the information given. You are adding
no information and it will be difficult to know what
to make of P-values and figures of model merit.
I would create a time variable which is just
year/5 and then -tsset- and model in terms of that.
If you really want to do this, there isn't a wired-in
Stata solution, but you can get there fairly quickly:
expand 5
bysort country year: replace year = year[1] + _n - 1
replace edu = . if mod(year, 5)
bysort country (year): ipolate edu year, gen(edu2)
I have some panel data on educational attainment which is organized in
5-year intervals.
(e.g.
country year edu
UK 1960 10
UK 1965 20
.
.
USA 1960 12
USA 1965 15
etc.)
However, for the particular model I want to estimate, I also need
observations in between the intervals (i.e. for 1961, 1962,...).
Therefore, I would like to "create" these observations by
"extrapolating" them "linearly".
