我用lp法算全要素生产率,D代表产出,用营业收入来衡量;K代表资本投入,用固定资产净额来衡量;L代表劳动投入,用企业当年员工总数来衡量;M代表中间投入,用购买商品、接受劳务所支付的现金来衡量;
. levpet lnd ,free(lnl) proxy(lnm) capital(lnk) i(id) t(year)
..................................................
Levinsohn-Petrin productivity estimator
Dependent variable represents value added. Number of obs = 10969
Group variable (i): id Number of groups = 904
Time variable (t): year
Obs per group: min = 8
avg = 12.1
max = 13
------------------------------------------------------------------------------
lnd | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
lnl | .1834794 .0147591 12.43 0.000 .1545522 .2124066
lnk | .3122406 .041718 7.48 0.000 .2304749 .3940064
------------------------------------------------------------------------------
Wald test of constant returns to scale: Chi2 = 154.76 (p = 0.0000).
.
. predict tfp_lp,omega
。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。
这里的Wald test of constant returns to scale: Chi2 = 154.76 (p = 0.0000).是为什么?怎么解决?我的P值都为0,正常吗?