运行simplest DSGE程序：

var x y;
varexo e;
parameters rho beta;
beta=0.9;
rho=0.9;
model(linear);
y=beta*y(+1)+x;
x=rho*x(-1)+e;
end;
initval;
x=0;
y=0;
end;
steady;
check;
resid;
shocks;
var e;stderr 0.1;
end;
stoch_simul(periods=900,order=1,irf=40,drop=400,aim_solver) y x;

save Simul_data y x;
varobs y x;
estimated_params;
beta, 0.8, 0.01, 0.99;
rho, 0.8, 0.01, 0.99;
end;
estimation(datafile=Simul_data, mode_check,
prefilter=1, order=1, mode_compute=1) y x;



一直提示：错误使用 initial_estimation_checks (line 49)
initial_estimation_checks:: Estimation can't take place because there are less declared shocks than observed variables!请大神帮助，感激不尽。。。。。