My suggestion for this table:
\documentclass{article}
\begin{document}
Text.
\begin{table}[h]
\sffamily
\begin{tabular}{r|*{12}{r}}
& \multicolumn{12}{l}{Development year}\\
U/W year & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 & 11 & 12 \\
\hline
2001 & n & n & n & n & n & n & n & n & n & n & n & n\\
2002 & n & n & n & n & n & n & n & n & n & n & n & \\
2003 & n & n & n & n & n & n & n & n & n & n & & \\
2004 & n & n & n & n & n & n & n & n & n & & & \\
2005 & n & n & n & n & n & n & n & n & & & & \\
2006 & n & n & n & n & n & n & n & & & & & \\
2007 & n & n & n & n & n & n & & & & & & \\
2008 & n & n & n & n & n & & & & & & & \\
2009 & n & n & n & n & & & & & & & & \\
2010 & n & n & n & & & & & & & & & \\
2011 & n & n & & & & & & & & & & \\
2012 & n & & & & & & & & & & & \\
& & & & & & & & & & & & \\
\hline
link ratios: & a & b & c & d & e & f & g & h & i & j & k & %l
\end{tabular}
\end{table}
Text.
\end{document}
Within the "fine tuning", I noticed that cells in lines 2 and 3-16 are both right-aligned, but with different right margins: write a comment if you wish to reproduce that effect precisely.