执行
*IV Probit - First Stage Coefficients
xi: ivprobit emp_m $control_m (age_gap = fine) if _est_bench == 1, twostep first
然后就出现
. *IV Probit  
. eststo ivprobit: xi: ivprobit emp_m $control_m (age_gap = fine) if _est_bench == 1,
>  cluster(wave_t1_m_group)
i.birth_order     _Ibirth_ord_1-4     (naturally coded; _Ibirth_ord_1 omitted)
i.wave            _Iwave_1989-2011    (naturally coded; _Iwave_1989 omitted)
i.t1_m            _It1_m_11-55        (naturally coded; _It1_m_11 omitted)
option cluster(wave_t1_m_group) not allowed