Hi there,

I am using a version of Stata 13.

I am running an SVAR model with four variables with the following identification scheme for Matrix A and B:

Code:
  
matrix A1 = (1,.,.,.\.,1,.,0\0,0,1,0\0,0,0,1)
matrix B1 = (.,0,0,0\ 0,.,0,0 \ 0,0,.,0\0,0,0,.) 

svar x1 x2 x3 x4, lags(1/2) aeq(A1) beq(B1)

Stata runs the maximum number of iterations (1600) before declaring that "convergence not achieved". For the last remaining few thousand iterations the log-likelihood has not changed and Stata tells me that each iteration is "(not concave)".

Stata does however give me a set of results on which I can perform impulse response functions. All the coefficients, apart from one, have standard errors and t values, and the impulse response functions fit with my theoretical predictions. Only one coefficient within the A matrix (the contemporaneous impact of x2 on x1, or "a_1_2" ) does not have a standard error or a t value, even though I do get a number for this coefficient.
  • Is it still possible to use these results?
  • Are the impulse response functions still meaningful?
  • And if not, can you please give me a rough indication why?
Thanks very much for your help.

All the best,
Ben