How to make table columns the same width?

Some suggestions:

• Align the numbers in the three data columns on their respective decimal markers. This may be done with the D column type provided by the dcolumn package. Adopting this method automatically makes the column widths equal.

• Impose more visual structure on the header material.

• Use the macro \addlinespace (provided by the booktabs package) instead of all-blank lines to increase vertical spacing where needed.

\documentclass{article} % or some other suitable document class \usepackage{caption} \captionsetup[table]{justification=centering, labelsep=newline, font=bf, skip=1ex} \usepackage{booktabs,threeparttable} \usepackage[T1]{fontenc} %new code: \usepackage{dcolumn} \newcolumntype{d}[1]{D..{#1}} \newcommand\mc[1]{\multicolumn{1}{c}{#1}} % handy shortcut macros \newcommand\mcx[1]{\multicolumn{1}{c@{}}{#1}} % for use in final column \begin{document} \begin{table}[ht] \centering \begin{threeparttable} \footnotesize % why? \caption{Optimism} \label{tab:optimism} \begin{tabular}{@{} l *{3}{d{4.6}} @{}} \toprule &\multicolumn{3}{c@{}}{Recommendation} \\ \cmidrule(l){2-4} & \mc{Hold} & \mc{Underperform} & \mcx{Sell} \\ & \mc{(1)} & \mc{(2)} & \mcx{(3)} \\ \midrule X1 & -0.022^{***} & -0.021^{***} & -0.019^{***} \\ & (-3.274) & (-3.257) & (-3.042) \\ \addlinespace X2 & 0.007^{***} & 0.007^{***} & 0.008^{***} \\ & (3.005) & (3.161) & (5.149) \\ \addlinespace X3 & 0.008 & 0.016 & 0.017 \\ & (0.123) & (0.250) & (0.299) \\ \addlinespace X4 & 0.039^{*} & 0.039^{*} & 0.034^{*} \\ & (1.830) & (1.823) & (1.803) \\ \addlinespace X5 & 0.004 & 0.005 & 0.004 \\ & (0.826) & (1.058) & (1.056) \\ \addlinespace Year FEs & \mc{Y} & \mc{Y} & \mcx{Y}\\ Firm FEs & \mc{Y} & \mc{Y} & \mcx{Y}\\ No.\ of Obs. & \mc{71,060} & \mc{71,060} & \mcx{71,060} \\ \bottomrule \end{tabular} \smallskip We report $t$-statistics in parentheses. *, **, and *** denote significance at the 10\%, 5\%, and 1\% levels, respectively. \end{threeparttable} \end{table} \end{document} 

As supplement to nice @mico answer (+1), with use of the tabularray package. It has longer table preamble, but shorter table body:

\documentclass{article} \usepackage{tabularray} \UseTblrLibrary{booktabs,siunitx} \ExplSyntaxOn \NewChildSelector{eachtwo} { \int_step_inline:nnnn {5}{2}{\l_tblr_childs_total_tl} { \clist_put_right:Nn \l_tblr_childs_clist {##1} } } \ExplSyntaxOff \usepackage{caption} \captionsetup[table]{justification=centering, labelsep=newline, font=bf, } \begin{document} \begin{table}[ht] \centering \NewTblrTheme{captionof}% { \DefTblrTemplate{caption}{default}% {\addtocounter{table}{-1}% \captionof{table}{\InsertTblrText{caption}}} } \SetTblrStyle{remark}{font=\footnotesize} \captionsetup[table]{skip=-0.5ex} \sisetup{ input-open-uncertainty =, input-close-uncertainty=, table-align-text-before=false, table-format={(}-1.3{***} } \begin{talltblr}[ theme = captionof, caption = {Optimism}, label = {tab:optimism}, remark{Note} = {We report $t$-statistics in parentheses. *, **, and *** denote significance at the \qty{10}{\%}, \qty{5}{\%}, and \qty{1}{\%} levels, respectively.} ]{colspec = {@{} l *{3}{Q[c, si]} @{}}, row{1-2}= {guard}, row{4-Z}= {rowsep=0 pt}, row{eachtwo} = {abovesep=1ex}, } \toprule &\SetCell[c=3]{c} Recommendation \\ \cmidrule{2-4} & {Hold\\ (1)} & {Underperform\\ (2)} & {Sell\\ (3)} \\ \midrule X1 & -0.022\TblrNote{***} & -0.021\TblrNote{***} & -0.019\TblrNote{***} \\ & (-3.274) & (-3.257) & (-3.042) \\ X2 & 0.007\TblrNote{***} & 0.007\TblrNote{***} & 0.008\TblrNote{***} \\ & (3.005) & (3.161) & (5.149) \\ X3 & 0.008 & 0.016 & 0.017 \\ & (0.123) & (0.250) & (0.299) \\ X4 & 0.039\TblrNote{*} & 0.039\TblrNote{*} & 0.034\TblrNote{*} \\ & (1.830) & (1.823) & (1.803) \\ X5 & 0.004 & 0.005 & 0.004 \\ & (0.826) & (1.058) & (1.056) \\ Year FEs & {Y} & {Y} & {Y} \\ Firm FEs & {Y} & {Y} & {Y} \\ No. of Obs. & {71,060} & {71,060} & {71,060} \\ \bottomrule \end{talltblr} \end{table} \end{document}