Hello everyone,

I'm currently wrestling with the use of instrumental variables in the SPLM
package in R.  From the documentation and looking at the code, I think I
may be having a reference problem with my instrumental and endogenous
variables, but I have yet to figure out the solution.  The code is as
follows:

formula <- polity_2 ~ gdpcapppp + pivagdp + trade + civil_war +
regionaldiffusion + regionalgrowthdiffusion + regionaldevelopmentdiffusion
+ edu
instr <- c("Coaly.Oil", "Lacustrine.Oil", "Shallow.Marine.Oil",
                 "Deep.Marine.Oil")
mod.1.est <- spgm(formula,
                  data=mod.1.splm,
                  listw=dist.neighbors,
                  model="within",
                  lag=FALSE,
                  endog="total_oil_income_pc",
                  instruments=instr,
                  verbose=TRUE,
                  spatial.error=TRUE,
                  method="w2sls"
  )

And I get the following error message:

Error in sperrorgm(formula = formula, data = data, index = index, listw =
listw,  :
  The model is not identified: Not enough instruments specified

I'm not sure if this is actually some kind of result (i.e., my instrumental
variables explain too little of the variance of the endogenous variable),
or if there is something wrong with the way I'm referencing the
instrumental variables.  I did try including the instrumental variables as
a matrix, to see if that fixed the problem, but the results were the same.
 Traceback() was unfortunately not particularly helpful in diagnosing this
problem.  Any advice would be greatly appreciated!

Thanks,
Caleb

-- 
Caleb Gallemore
Ph.D. Student
Department of Geography
The Ohio State University

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