\begin{table}%t1
\caption{\label{table_Npaires}Number of pairs with $\Delta M_B^{\rm max} = 1.5$ and $M_B < -18 - Q(z)$. In brackets the number of triplets is given.}
\par
%\centering
\small
\begin{tabular}{c c c c c}
\hline\hline
%&&&& \\[-8pt]
  & $20~h^{-1}~{\rm kpc}$  & $30~h^{-1}~{\rm kpc}$ & $50~h^{-1}~{\rm kpc}$ & $100~h^{-1}~{\rm kpc}$\\ 
  \hline 
%&&&& \\[-8pt]
 500 km~s$^{-1}$ & 36 (0) & 51 (0) & 102 (6) & 202 (22)\\  
1000 km~s$^{-1}$ & 48 (0) & 68 (0) & 131 (10) & 267 (32)\\ 
2000 km~s$^{-1}$ & 50 (0) & 73 (0) & 143 (13) & 314 (46)\\ 
\hline
\end{tabular} 
\end{table}