Panel Data - Identical Cross Section Values-UnitRoot test

[Kario90]

Hello, my first post here.

Using FE panel data, I am regressing economic growth on a set of variables for 149 countries, from 1996 to 2011. One of the regressors is the log of initial GDP per capita (1996), so for each cross section/country, there are 16 identical values.

Random numerical example:

Country Year GDP
Afghanistan 1996 400
Afghanistan 1997 400
...
Afghanistan 2011 400

and so on so forth.

When I try any unit root test for this variable, i get the ''insufficient number of observations encountered in Uroot ́ ́error.

Could this be a simple case of literally not enough observations (hard to believe, 2384 obs should be ok) or could it be a general specification problem?

Thank you in advance!

[JessieXiao]

I met the same problem.