> I have a yearly gross product data and I would like to transform to
> montly data.
>
> Is there a program to do it?
You may be looking for something like the Chow-Lin procedure.
(Google it, and/or "disaggregation".) It uses higher-frequency
series that are conceptually correlated with your lower-frequency
series (e.g. GDP) to make imputations about the hypothetical higher-
frequency values of that series. I know a procedure to do so has
been implemented in RATS; I have seen papers reference Gauss
programs that implement it; to the best of my knowledge it has not
been programmed in Stata. There is a literature on this topic that
you should explore, and some authors have suggested alternatives.
The World Bank's preferred method is the Denton procedure; findit denton within Stata. That only alters the frequency by one, though-- from annual to quarterly, or from quarterly to monthly. I agree with Michael that going from annual to monthly is likely to be befraught with problems. I would recommend using an available monthly series as a proxy, ignoring the GDP figures. A popular choice is an industrial production index.
Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html
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