那些it和it-1都是下角标，不知怎么的格式没过去

xtabond2 y l.y l(0/1).(rd l ip) year*,gmm(l.(y l rd)) iv(year*,equation(level)) robust small
Favoring space over speed. To switch, type or click on mata: mata set matafavor speed, perm.
Warning: Number of instruments may be large relative to number of observations.
Warning: Two-step estimated covariance matrix of moments is singular.
Using a generalized inverse to calculate robust weighting matrix for Hansen test.
Difference-in-Sargan/Hansen statistics may be negative.

Dynamic panel-data estimation, one-step system GMM

Group variable: city_dum                        Number of obs      =       210
Time variable : year                            Number of groups   =        30
Number of instruments = 83                      Obs per group: min =         7
F(8, 29)      =    624.36                                      avg =      7.00
Prob > F      =     0.000                                      max =         7

Robust
y       Coef.   Std. Err.      t    P>t     [95% Conf. Interval]

y
L1.    .9294596   .0484361    19.19   0.000     .8303965    1.028523
            
rd
--.    .2459836   .0870797     2.82   0.008     .0678857    .4240816
L1.   -.0663017   .0515252    -1.29   0.208    -.1716825    .0390792
            
l
--.   -.6440051   .1009373    -6.38   0.000     -.850445   -.4375652
L1.    .5511354   .0761284     7.24   0.000     .3954353    .7068356
            
ip
--.   -.0553142   .0638734    -0.87   0.394      -.18595    .0753215
L1.    .0258019   .0495284     0.52   0.606    -.0754949    .1270988
            
year   -.0638999    .009686    -6.60   0.000    -.0837099   -.0440899
_cons     127.703   19.15473     6.67   0.000     88.52717    166.8788

Instruments for first differences equation
GMM-type (missing=0, separate instruments for each period unless collapsed)
L(1/7).(L.y L.l L.rd)
Instruments for levels equation
Standard
year
_cons
GMM-type (missing=0, separate instruments for each period unless collapsed)
D.(L.y L.l L.rd)

Arellano-Bond test for AR(1) in first differences: z =  -2.75  Pr > z =  0.006
Arellano-Bond test for AR(2) in first differences: z =   1.22  Pr > z =  0.224

Sargan test of overid. restrictions: chi2(74)   = 119.33  Prob > chi2 =  0.001
(Not robust, but not weakened by many instruments.)
Hansen test of overid. restrictions: chi2(74)   =  25.76  Prob > chi2 =  1.000
(Robust, but weakened by many instruments.)

Difference-in-Hansen tests of exogeneity of instrument subsets:
GMM instruments for levels
Hansen test excluding group:     chi2(56)   =  25.26  Prob > chi2 =  1.000
Difference (null H = exogenous): chi2(18)   =   0.50  Prob > chi2 =  1.000
iv(year, eq(level))
Hansen test excluding group:     chi2(73)   =  25.76  Prob > chi2 =  1.000
Difference (null H = exogenous): chi2(1)    =   0.00  Prob > chi2 =  0.998

谁能帮我看一下哪里出错了，工具变量数量怎么减少啊

请问输入数据的格式是什么样的呢