When I run this code and shock pop growth rate it never returns back. Does anyone know WHY?
var POP ; // ratio variables (derived)
varexo eps_pop ;
parameters g_pop rho_pop;
g_pop = 0.0015;
rho_pop = 0.9;
model;
// ---- demographics
diff(log(POP)) = rho_pop*diff(log(POP(-1))) + (1-rho_pop)*g_pop + eps_pop;
end;
initval;
POP = 42000;
end;
histval;
POP(0)=42000;
POP(-1)=42000/(1+g_pop);
POP(-2)=42000/(1+g_pop)^2;
end;
shocks;
var eps_pop; periods 1; values 0.003;// migration wave
end;
perfect_foresight_setup (periods=500);
perfect_foresight_solver;