\documentclass{article}
\begin{document}
\begin{table}
\small
\centering
\begin{tabular}{c|cc}
Source & Variation up (Stat. up) \% & Variation down (Stat. down) \% \\ \hline 
muR\_muF-Wjets\_SR2L & -1000.0 & 1000.0 \\ 
ckkw-Wjets\_SR2L & -1000.0 & 1000.0 \\ 
qsf-Wjets\_SR2L & -1000.0 & 1000.0 \\ 
muR\_muF-Wjets\_tW2L\_CRtt & -1000.0 & 1000.0 \\ 
ckkw-Wjets\_tW2L\_CRtt & -1000.0 & 1000.0 \\ 
qsf-Wjets\_tW2L\_CRtt & -1000.0 & 1000.0 \\ 
muR\_muF-Wjets\_tW2L\_CRttZ & -1000.0 & 1000.0 \\ 
ckkw-Wjets\_tW2L\_CRttZ & -1000.0 & 1000.0 \\ 
qsf-Wjets\_tW2L\_CRttZ & -1000.0 & 1000.0 \\ 
muR\_muF-Wjets\_tW2L\_CRWZ & -1000.0 & 1000.0 \\ 
ckkw-Wjets\_tW2L\_CRWZ & -1000.0 & 1000.0 \\ 
qsf-Wjets\_tW2L\_CRWZ & -1000.0 & 1000.0 \\ 
muR\_muF-Wjets\_tW2L\_VRtt & -1000.0 & 1000.0 \\ 
ckkw-Wjets\_tW2L\_VRtt & -1000.0 & 1000.0 \\ 
qsf-Wjets\_tW2L\_VRtt & -1000.0 & 1000.0 \\ 
muR\_muF-Wjets\_tW2L\_VR3L & -1000.0 & 1000.0 \\ 
ckkw-Wjets\_tW2L\_VR3L & -1000.0 & 1000.0 \\ 
qsf-Wjets\_tW2L\_VR3L & -1000.0 & 1000.0 \\ 
\end{tabular}
\end{table}
\end{document}
