Dear everyone,

I am working on my masters thesis and I am trying to make a twostep system gmm regression on gdp with a five-year average. I have calculated the average per five years in excel. My average for 1995-1999 is called 1995. I have 1995, 2000, 2005 2010 and 2015.
I specify my data as; xtset CountryID Year, and here delta is 1. When I try to run my regression stata tells me that there are no observations and I suspect it is due to the fact that four years are missing per each five-year average.

Please, does anyone know how I can solve this problem, perhaps I need to change delta to 5? But I do not know how to do so.

Any help is greatly appreciated!