求助大家为什么我的数据是平衡的，但是xthreg还是显示不平衡
tsset id t
       panel variable:  id (strongly balanced)
        time variable:  t, 1 to 4
                delta:  1 unit

. xthreg consum index lngdp payment , rx( income ) qx( fina_debt ) thnum(1) grid
> (400) trim(0.01) bs(500)
Panel threshold model need balanced panel, check your data!