Hi. I'm trying to estimate the natural interest rate. Unfortunately, I have run into the following complication:
This is the model:

Code:
tsset YEAR
constraint 1 [u1]n_t = 1
constraint 2 [u1]ar = 1
constraint 3 [u3]L.u3 = 1
constraint 4 [u3]L.u4 = 1
constraint 5 [u3]L.n_t = 1
constraint 6 [u4]L.u4 = 1
constraint 7 [u5]L.u5 = 1
constraint 8 [lne]u5 = 1
constraint 9 [lngdp]u3 = 1
sspace (u1 u4 n_t u2, state noerror noconstant) ///
(ar L.ar, state noconstant) ///
(u3 L.u3 L.u4 L.n_t, state noconstant) ///
(u4 L.u4, state noconstant) ///
(u5 L.u5, state noconstant) ///
(lngdp u3 L.lngdp-L.u3 L2.lngdp-L2.u3 L.rshi-L.u1+L2.rshi-L2.u1 L.lne-L2.lne, noconstant) ///
(pai L.pai L.lngdp-L.u3 L.lne-L.u5, nonconstant) ///
(lne u5 L.lngdp-L.u3, noconstant), ///
constraints(1/9) covstate(diagonal)



Hope anyone can share any thoughts and possible solutions about this problem.
Thank you very much.