Problem with \toprule: sometimes not bold

Question

I am using package booktabs and using \toprule, \bottomrule etc. in order to make bold lines.

The problem is that sometimes, using \toprule or \bottomrule, the lines drawn are bold but sometimes not! No error message appear, simply the lines are not bold. For instance the following table:

\begin{table}[H]
\caption{Placebo DID: 1999-2000}
\label{placebo}

\

\centering

\begin{adjustbox}{ max width=\textwidth}

\begin{tabular}{lccc} \toprule

 & A & B & C \\

& Participation Decision (Save) & Participation Decision (Save) & Participation Decision (Save) \\

 &  &Males  & Females  \\ \cmidrule(lr{.75em}){2-4}

 &  &  &  \\

After & 0.0286** & 0.0261** & 0.0285** \\

 & (0.0125) & (0.0115) & (0.0125) \\

Region & 0.00125 & -0.00479 & -0.000551 \\

 & (0.0195) & (0.0172) & (0.0195) \\

Treatment & 0.0343 & 0.0351 & 0.0345 \\

 & (0.0273) & (0.0244) & (0.0273) \\

Female & 0.0836*** &  &  \\

 & (0.0116) &  &  \\

Female (After) & -0.00238 &  &  \\

 & (0.0156) &  &  \\
Female (Scotland) & -0.00733 &  &  \\

 & (0.0239) &  &  \\

Female (Treat) & 0.000399 &  &  \\

 & (0.0336) &  &  \\

Constant & 0.395*** & 0.446*** & 0.461*** \\

 & (0.0568) & (0.0792) & (0.0811) \\

 **&  &  &  \\ \midrule**          

Observations & 15,264 & 8,393 & 6,871 \\

 R-squared & 0.111 & 0.102 & 0.131 \\ \bottomrule

\multicolumn{4}{c}{ Robust standard errors in parentheses} \\

\multicolumn{4}{c}{ *** p$<$0.01, ** p$<$0.05, * p$<$0.1} \\

\multicolumn{4}{c}{ Source: BHPS(2009)} \\

\end{tabular}

\end{adjustbox}
\end{table}

If I set midrule there, the lines of \toprule and \bottomrule are not bold anymore. Instead if I write \hline instead of \midrule, then both lines are bold. Same thing happens if I change max text width from 0.75 to 0.9! I truly do not understand!!!

Thank you for helping!:)

Answer 1

Your example works just fine. You should zoom in to see the correct rendering of the lines. Sometimes, the viewer is not able to handle every size. Especially as you are using some scaling. I would not recommend to scale your table but to reformat it in order to fit the page. Please see my suggestion below:

% arara: pdflatex

\documentclass{article}
\usepackage{caption}
\usepackage{float}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{siunitx}
\usepackage{etoolbox}
\robustify\tnote

\begin{document}
\begin{table}[H]
\centering
\begin{threeparttable}
    \caption{Placebo DID: 1999--2000}\label{placebo}
    \sisetup{%
        ,input-symbols         = ()
        ,table-space-text-post = ***
        ,table-align-text-post = false
        ,group-four-digits     = true
        }   
    \begin{tabular}{%
            l
            S[table-format=-1.6]
            S[table-format=-1.5]
            S[table-format=-1.6]
            }\toprule           
        & A & B & C \\          
        & \multicolumn{3}{c}{Participation Decision (Save)}  \\\cmidrule{2-4}           
        &  & {Males}  & {Females}  \\ \midrule          
        After & 0.0286\tnote{**} & 0.0261\tnote{**} & 0.0285\tnote{**} \\           
        & (0.0125) & (0.0115) & (0.0125) \\\addlinespace        
        Region & 0.00125 & -0.00479 & -0.000551 \\          
        & (0.0195) & (0.0172) & (0.0195) \\\addlinespace            
        Treatment & 0.0343 & 0.0351 & 0.0345 \\         
        & (0.0273) & (0.0244) & (0.0273) \\\addlinespace            
        Female & 0.0836\tnote{***} &  &  \\         
        & (0.0116) &  &  \\\addlinespace            
        Female  & -0.00238 &  &  \\         
        (After)& (0.0156) &  &  \\\addlinespace
        Female  & -0.00733 &  &  \\         
        (Scotland)& (0.0239) &  &  \\\addlinespace          
        Female  & 0.000399 &  &  \\         
        (Treat)& (0.0336) &  &  \\\addlinespace         
        Constant & 0.395\tnote{***} & 0.446\tnote{***} & 0.461\tnote{***} \\            
        & (0.0568) & (0.0792) & (0.0811) \\\midrule         
        Observations\tnote{**} & 15,264 & 8,393 & 6,871 \\          
        R-squared & 0.111 & 0.102 & 0.131 \\ \bottomrule                    
    \end{tabular}   
    \begin{tablenotes}[flushleft]
        \item Robust standard errors in parentheses
        \item[***] $p<0.01$
        \item[**\hphantom{*}] $p<0.05$
        \item[*\hphantom{**}] $p<0.1$
        \item Source: BHPS(2009)
    \end{tablenotes}    
\end{threeparttable}
\end{table}
\end{document}