Siunitx: Overfull hbox warnings when including significance stars.

Question

I use siunitx to decimal align the contents of tables that I create with Stata's estout, as shown in the MWE below. I think the output is perfect, with the numbers being aligned on the decimal point and "pseudo"-centered under the "ß / SE" and "Margin" columns.

The problem is that I get an overfull hbox warning for every single cell. I've played around with table-space-text-post to include the asterisk, but without any luck. Does anyone have a solution for this problem?

\documentclass{scrartcl}

\usepackage{lmodern}

\newcommand{\sym}[1]{\rlap{#1}}

\usepackage{siunitx}
\sisetup{
        detect-mode,
        tight-spacing               = true,
        group-digits                = false ,
        input-signs             = ,
        input-symbols               = ( ) - + *,
        input-open-uncertainty  = ,
        input-close-uncertainty = ,
        table-align-text-post   = false,
        % table-space-text-pre  = -,
        % table-space-text-post = *
        }

\usepackage{booktabs}

\begin{document}
\begin{tabular*}
{\textwidth}{@{\hskip\tabcolsep\extracolsep\fill}l*{3}{S[table-format=1.3,table-column-width=11mm]S[table-format=1.3,table-column-width=11mm]}}
\toprule
&\multicolumn{2}{c}{(1)}                    &\multicolumn{2}{c}{(2)}                    &\multicolumn{2}{c}{(3)}                    \\
&\multicolumn{2}{c}{Column One}              &\multicolumn{2}{c}{Column Two X}&\multicolumn{2}{c}{Column Three XX}\\
&\multicolumn{1}{c}{$\beta$ / SE}         &\multicolumn{1}{c}{Margin}         &\multicolumn{1}{c}{$\beta$ / SE}         &\multicolumn{1}{c}{Margin}         &\multicolumn{1}{c}{$\beta$ / SE}         &\multicolumn{1}{c}{Margin}         \\
\midrule
\hspace{0.1cm} 18--24&      -0.176         &      -0.044         &      -0.256         &      -0.047         &      -0.820\sym{***}&      -0.101\sym{***}\\
                    &     (0.152)         &                     &     (0.188)         &                     &     (0.310)         &                     \\
\hspace{0.1cm} 25--34&       0.067         &       0.017         &       0.047         &       0.009         &      -0.046         &      -0.006         \\
\bottomrule
\addlinespace[.75ex]
\end{tabular*}
\end{document}

Answer 1

If you want to have space reserved for something after the number part in an S column, you will need to reserve appropriate space using table-space-text-post. A slight awkwardness arises as the array package treats * as 'special', so you need braces here:

\documentclass{article}

\usepackage{siunitx}

\begin{document}
\begin{tabular}{S[ table-format = -1.3, table-space-text-post = {***}]}
  -0.101***
\end{tabular}

\end{document}

If you are using a custom command (here \sym) in an S column, it really needs to be engine-protected. For that, the \NewDocumentCommand command from xparse is recommended:

\documentclass{article}

\usepackage{siunitx}

\NewDocumentCommand{\sym}{m}{#1}

\begin{document}
\begin{tabular}{S[table-format = -1.3, table-space-text-post = \sym{***}]}
  -0.101\sym{***}
\end{tabular}

\end{document}