Two period Data & Issues of Lag

[Melkamu Delju]

Dear sir/ madam,

I am working on two period data, Ethiopian Enterprise survey obtained from the World Bank micro data, to see the relationship between innovation and firm performance in Ethiopian context. Though it is two period data (each reporting innovation outcomes during the period 3 years before each wave), there is only one. I am wondering why? Here is what I did. For your info here is xttab result. Thank you for your help.

. xtreg prdctvty prdctI l.prdctI
no observations
r(2000);


. xttab prdctI

Overall Between Within
prdctI | Freq. Percent Freq. Percent Percent
----------+-----------------------------------------------------
No | 899 60.46 782 69.88 90.09
Yes | 588 39.54 492 43.97 84.25
----------+-----------------------------------------------------
Total | 1487 100.00 1274 113.85 87.83
(n = 1119)

[Nick Cox]

Your xtset or tsset setting probably means that lag 1 would be the previous year. Perhaps you need to add delta(3). See the help for either command.