Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: xtabond and no observations


From   Kit Baum <[email protected]>
To   [email protected]
Subject   st: xtabond and no observations
Date   Tue, 7 Dec 2004 13:36:39 -0500

Jo had this problem with her third-world data, which is a panel with unequally spaced waves. Monica suggested

replace time2 = 1 if d73 == 1 ;
replace time2 = 2 if d78 == 1 ;
replace time2 = 3 if d83 == 1 ;
replace time2 = 4 if d88 == 1 ;
replace time2 = 5 if d93 == 1 ;
replace time2 = 6 if d98 == 1 ;

tsset panchayat time2 ;


While this will technically work, one should be VERY careful. Given that Jo's observations differ in their timing by two years (86, 88, ... 96), [as opposed to Monica's, which appear to be quinquennia] keep in mind that the xtabond estimator is based on differencing the time series (which is why there were 'no observations' -- a biannual series on an annual calendar has no defined first differences). Creating a time variable in which t+1 = 2 years down the road is fine, but you want to be very careful not to interpret any findings in 'per annum' terms, since for this dataset one unit of time = 2 calendar years. For instance, if anything in the model ends up being an estimate of a growth rate, it should be decompounded to annual for comparison.

Kit Baum, Boston College Economics
http://ideas.repec.org/e/pba1.html

*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/




© Copyright 1996–2024 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index