I would like for columns A1, A3 and B1 to be more like column B3, which doesn't have any cell padding on the side facing out of its group.
Can I achieve that? The code I have right now looks like this:
\documentclass{article}
\usepackage{booktabs}
\begin{document}
\begin{table*}\centering
\begin{tabular}{@{}lccccccc@{}}\toprule
& \multicolumn{3}{c}{A} & \phantom{abc}& \multicolumn{3}{c}{B}\\ \cmidrule{2-4} \cmidrule{6-8}
& 1 & 2 & 3 && 1 & 2 & 3\\
\midrule
C & 0.60 & 0.951 & 0.245 & & 1.151 & 1.563 & 0.586 \\
& (0.262) & (0.364) & (0.310) & & (0.620) & (0.905) & (0.696) \\
\midrule
\(N\) & 919629 & 468093 & 451536 & & 186271 & 94771 & 91500 \\
\bottomrule
\end{tabular}
\end{table*}
\end{document}
\cmidrule
extends further to right in the A3 column than in the B3 column. If removing the empty column would help resolve my issue, then I am open to that.@{}
in your table. however, see answers below for more "sophisticated" solutions :-)