\begin{tabular}{|p{4.25em}|p{15.125em}|p{12.315em}|p{8.565em}|}
\toprule
\textbf{Variables} & \textbf{Definition} & \textbf{Formula} & \textbf{Source} \\
\midrule
Credit Risk & A borrower is unable to repay the loan or interest on the loan is termed as credit risk. & Non-performing loan / Total Loan & \multicolumn{1}{l|}{} \\
\midrule
GDP Growth & GDP (Gross Domestic Product) growth measures how fast an economy is growing by comparing GDP of two quarters. & (Current year growth rate - Previous year growth rate) / Current year growth rate & (Boudriga, Taktak, \& Jellouli, 2010; Djiogap \& Ngomsi, 2012) \\
\midrule
Inflation Rate Growth & The rate at which prices of goods increases overtime decreasing the value of money. & (Current price index - Previous year price index / Previous year price index) *100 & (I. Khan et al., 2018) \\
\midrule
Interest Rate & The percentage amount charged by the bank for lending money to the party. & Interest = (Principal + Annual Rate + Loan Period) / 100 & (Hui et al., 2017)\\
\midrule
Capital Adequacy Ratio & It is a measure of bank's total available capital divided by risk weighted assets. & Total capital / Risk-weighted asset & (Boudriga et al., 2010; Kasana \& Naveed, 2016; Poudel, 2012) \\
\midrule
Loan to Total Asset Ratio & The ratio checks the of banks' assets by taking outstanding loans as a percentage of its assets. & (Total Outstanding Debt / Total Assets) *100 & (Ahmadyan, 2018) \\
\midrule
Loan to Deposit Ratio & This ratio checks the liquidity of a bank through comparison of its total loans and total deposits. & Total loan / Total deposits & (Kasana \& Naveed, 2016) \\
\midrule
Return on Assets & It is to check the profitability of banks & Total Income / Total Assets & (Boudriga 2010; Kasana,Naveed,2016)\\
\midrule
Bank Size & Natural logarithm of total assets of bank in time t. & Log of bank assets & (Garr, 2013; Kasana \& Naveed, 2016) \\
\bottomrule
\end{tabular}%
\label{tab:addlabel}%
\end{table}
答案1
删除所有垂直线和大部分水平线，这对你自己，尤其是你的读者来说，都是一个很大的好处。这种改变的结果将是一个更加开放的表格“外观”，并且字面上邀请让读者停留片刻并花一些时间来消化你所收集的信息。
另外：我已经修正了你的 GDP 增长公式；还有很多其他变量定义和公式需要修正。例如，人们通常对通货膨胀率感兴趣，而不是通货膨胀率的增长率。
\documentclass{article}
\usepackage[letterpaper,margin=1in]{geometry} % set suitable page parameters
\usepackage{booktabs}
\usepackage{array,ragged2e}
\newcolumntype{P}[1]{>{\RaggedRight\arraybackslash}p{#1}}
\begin{document}
\begin{table}
\centering
\caption{Variable Definitions\strut}
\label{tab:addlabel}
\begin{tabular}{@{} P{5.25em}P{15.125em}P{12.315em}P{8.565em} @{}}
\toprule
\textbf{Variables} & \textbf{Definition} & \textbf{Formula} & \textbf{Source} \\
\midrule
Credit Risk & A borrower is unable to repay the loan or interest on the loan is termed as credit risk. & Non-performing loan\slash Total Loan & \\
\addlinespace
GDP Growth & GDP (Gross Domestic Product) growth measures how fast an economy is growing by comparing GDP of two quarters. & (Current year GDP~$-$ Previous year GDP)\slash Current year GDP & Boudriga, Taktak, \& Jellouli, 2010; Djiogap \& Ngomsi, 2012 \\
\addlinespace
Inflation Rate Growth & The rate at which prices of goods increases overtime decreasing the value of money. & (Current price index~$-$ Previous year price index\slash Previous year price index) *100 & I. Khan et al., 2018 \\
\addlinespace
Interest Rate & The percentage amount charged by the bank for lending money to the party. & Interest = (Principal + Annual Rate + Loan Period)\slash 100 & Hui et al., 2017\\
\addlinespace
Capital Adequacy Ratio & It is a measure of bank's total available capital divided by risk weighted assets. & Total capital\slash Risk-weighted asset & Boudriga et al., 2010; Kasana \& Naveed, 2016; Poudel, 2012 \\
\addlinespace
Loan to Total Asset Ratio & The ratio checks the of banks' assets by taking outstanding loans as a percentage of its assets. & (Total Outstanding Debt\slash Total Assets) *100 & Ahmadyan, 2018 \\
\addlinespace
Loan to Deposit Ratio & This ratio checks the liquidity of a bank through comparison of its total loans and total deposits. & Total loan\slash Total deposits & Kasana \& Naveed, 2016 \\
\addlinespace
Return on Assets & It is to check the profitability of banks & Total Income\slash Total Assets & Boudriga 2010; Kasana \& Naveed, 2016\\
\addlinespace
Bank Size & Natural logarithm of total assets of bank in time $t$. & Log of bank assets & Garr, 2013; Kasana \& Naveed, 2016 \\
\bottomrule
\end{tabular}
\end{table}
\end{document}
答案2
如果您确实想添加与 兼容的垂直规则booktabs（即使这不符合 的精神booktabs），您可以使用{NiceTabular}。nicematrix但是，我认为没有这些规则效果会更好。
\documentclass{article}
\usepackage{nicematrix}
\usepackage{booktabs}
\begin{document}
\begin{table}
\begin{NiceTabular}{p{4.25em}p{15.125em}p{12.315em}p{8.565em}}[vlines]
\toprule
\textbf{Variables} & \textbf{Definition} & \textbf{Formula} & \textbf{Source} \tabularnewline
\midrule
Credit Risk & A borrower is unable to repay the loan or interest on the loan is termed as credit risk. &
Non-performing loan / Total Loan \tabularnewline
\midrule
GDP Growth & GDP (Gross Domestic Product) growth measures how fast an economy is growing by comparing GDP of
two quarters. & (Current year growth rate - Previous year growth rate) / Current year growth rate & (Boudriga,
Taktak, \& Jellouli, 2010; Djiogap \& Ngomsi, 2012) \tabularnewline
\midrule
Inflation Rate Growth & The rate at which prices of goods increases overtime decreasing the value of money. &
(Current price index - Previous year price index / Previous year price index) *100 & (I. Khan et al., 2018) \tabularnewline
\midrule
Interest Rate & The percentage amount charged by the bank for lending money to the party. & Interest =
(Principal + Annual Rate + Loan Period) / 100 & (Hui et al., 2017)\tabularnewline
\midrule
Capital Adequacy Ratio & It is a measure of bank's total available capital divided by risk weighted assets. &
Total capital / Risk-weighted asset & (Boudriga et al., 2010; Kasana \& Naveed, 2016; Poudel, 2012) \tabularnewline
\midrule
Loan to Total Asset Ratio & The ratio checks the of banks' assets by taking outstanding loans as a percentage
of its assets. & (Total Outstanding Debt / Total Assets) *100 & (Ahmadyan, 2018) \tabularnewline
\midrule
Loan to Deposit Ratio & This ratio checks the liquidity of a bank through comparison of its total loans and
total deposits. & Total loan / Total deposits & (Kasana \& Naveed, 2016) \tabularnewline
\midrule
Return on Assets & It is to check the profitability of banks & Total Income / Total Assets & (Boudriga 2010;
Kasana,Naveed,2016)\tabularnewline
\midrule
Bank Size & Natural logarithm of total assets of bank in time t. & Log of bank assets & (Garr, 2013; Kasana \&
Naveed, 2016) \tabularnewline
\bottomrule
\end{NiceTabular}%
\label{tab:addlabel}%
\end{table}
\end{document}