\begin{tabular}{lrrr}
\toprule
            & \multicolumn{2}{c}{SepalLength} & \multicolumn{1}{c}{Counts} \\ 
\cmidrule(lr){2-3} \cmidrule(lr){4-4} 
            &      (1) &                  (2) &                        (3) \\ 
\midrule
(Intercept) & 6.526*** &             3.457*** &                   3.045*** \\ 
            &  (0.479) &              (0.309) &                    (0.126) \\ 
SepalWidth  &   -0.223 &             0.399*** &                            \\ 
            &  (0.155) &              (0.091) &                            \\ 
PetalWidth  &          &             0.972*** &                            \\ 
            &          &              (0.052) &                            \\ 
Outcome: B  &          &                      &                     -0.454 \\ 
            &          &                      &                    (0.202) \\ 
Outcome: C  &          &                      &                     -0.293 \\ 
            &          &                      &                    (0.193) \\ 
\midrule
Estimator   &      OLS &                  OLS &                         NL \\ 
\midrule
$N$         &      150 &                  150 &                          9 \\ 
$R^2$       &    0.014 &                0.707 &                            \\ 
\bottomrule
\end{tabular}
