Dear All,

I have a panel dataset with 18,071 observations.

I am estimating the following model in stata:

xtivreg2 ret2_w mret2_w s_r10_lmcap s_r10_bm s_r10_mom s_r10_op_prof s_r10_agro s_r10_stdret s_r10_vol_s s_r10_lag_ue_p s_r10_lnumage s_r10_divy yr1-yr13 (tq2_centered_w = wklymret_w wklych_usd_w) if sample_to_use == 3, fe first liml cluster(cnum) endog(tq2_centered_w)

The output begins with the warning:

Warning - singleton groups detected. 194 observation(s) not used.

Partial output below indicates 17,877 observations were used (18071-194 = 17877)

Number of clusters (cnum) = 1132 Number of obs = 17877
F( 25, 1131) = 59.19
Prob > F = 0.0000
Total (centered) SS = 56.71687777 Centered R2 = -0.1134
Total (uncentered) SS = 56.71687777 Uncentered R2 = -0.1134
Residual SS = 63.15058851 Root MSE = .06141

When I check generate descriptive statistics, I have complete data for all the variables in the above model for 18,071 observations. No missing values.

Importantly, I have only 7 singletons in my 18071-observation dataset:

. count if number == 1 & sample_to_use == 3
7

I would like to drop the 194 singletons. Could some one let me know how to identify and eliminate the 194 observations?

Best,

Srinivasan Rangan