[Tex/LaTex] Longtable is not centered

horizontal alignmentlongtabletables

I have this very wide long table. Even though I have included {c}, the table does not appear centered.
This is the code:

\documentclass[12pt]{article}
\begin{document}    
\begin{longtable}[c]{lcccccccc}
        \label{my-label}\\
        \toprule
        \multicolumn{1}{l}{\textbf{Descriptive Statistic}} & \multicolumn{1}{c}{\textbf{$rtb_t$}} & \multicolumn{1}{c}{\textbf{$xIG_t$}} & \multicolumn{1}{c}{\textbf{$xHY_t$}} & \multicolumn{1}{c}{\textbf{$xEM_t$}} & \multicolumn{1}{c}{\textbf{$xConv_t$}}& \multicolumn{1}{c}{\textbf{$y_t$}}& \multicolumn{1}{c}{\textbf{$DefRate_t$}}& \multicolumn{1}{c}{\textbf{$spr_t$}}\\
        \endfirsthead
        %
        \endhead
        %
        \toprule
        ~~Mean  &  0.1658  &   0.0378  &   0.0442  &   0.0502   &  0.0524  &   0.4233  &   0.4996   &  0.2521 \\
        ~~Standard Deviation & 0.0459  &   0.0699  &   0.0928 &    0.0810   &  0.1250  &   0.0439  &   0.0909   &  0.0351 \\
        ~~Variance & 0.0021  &   0.0049  &   0.0086 &    0.0066  &   0.0156  &   0.0019  &   0.0083  &   0.0012\\
        ~~Skewness & 0.1963  &  -0.9932  &  -1.6310  &  -4.7227 &   -1.1165  &   0.1730 &    1.2201   &  2.8841\\
        ~~Kurtosis & 2.9890 &    8.4808  &  14.6628  &  50.1189  &   8.5597  &   2.0001  &   3.7574  &  13.6014 \\
        ~~Sharpe Ratio &  -  &   0.5404  &   0.4762  &   0.6192  &   0.4191  &   -   &  - &   -\\
        \bottomrule       
        \caption{Sample Statistics: Bond Model}
    \end{longtable}
\end{document}

This is the result

enter image description here

I would like to center it, but I am not able. Thanks for your help.

Best Answer

Playing with the fontsize and the value of \tabcolsep is enough. In addition, I used the S column type, for the alignment of the numeric cells on the decimal dot (non numeric cells are centred if you enclose their content between braces), and I moved the caption above the table, which is the typographic tradition for tables, especially with tables that can extend over several pages.:

\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{longtable, booktabs}
\usepackage{siunitx}

\begin{document}

{\footnotesize\setlength{\tabcolsep}{3pt}
\sisetup{table-format=2.4}
\begin{longtable}{l*{8}{S}}
    \caption{Sample Statistics: Bond Model}
    \label{my-label}\\
    \toprule
  \textbf{Descriptive Statistic} &{$rtb_t$} & {$xIG_t$} & {$xHY_t$} & {$xEM_t$} & {$xConv_t$} & {$y_t$}& {$DefRate_t$} & {$spr_t$}\\
    \endfirsthead
    %
    \endhead
    %
    \toprule
    Mean & 0.1658 & 0.0378 & 0.0442 & 0.0502 & 0.0524 & 0.4233 & 0.4996 & 0.2521 \\
    Standard Deviation & 0.0459 & 0.0699 & 0.0928 & 0.0810 & 0.1250 & 0.0439 & 0.0909 & 0.0351 \\
    Variance & 0.0021 & 0.0049 & 0.0086 & 0.0066 & 0.0156 & 0.0019 & 0.0083 & 0.0012\\
    Skewness & 0.1963 & -0.9932 & -1.6310 & -4.7227 & -1.1165 & 0.1730 & 1.2201 & 2.8841\\
    Kurtosis & 2.9890 & 8.4808 & 14.6628 & 50.1189 & 8.5597 & 2.0001 & 3.7574 & 13.6014 \\
    Sharpe Ratio &{–} & 0.5404 & 0.4762 & 0.6192 & 0.4191 & {–} & {–} & {–} \\
    \bottomrule
\end{longtable}}

\end{document}

enter image description here

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