\begin{table}%t4
 \caption{Proper motions$^\dagger$ in the S5 polar cap sample.}
  \label{tab:proper_motion}
%\centerline
{
 \begin{tabular}{ccrr}
   \hline\hline
  \multicolumn{1}{c}{\rm Source} & 
  \multicolumn{1}{c}{\rm Comp.} & 
  \multicolumn{1}{c}{$\mu$} & 
  \multicolumn{1}{c}{$\beta_{\rm app}$} \\ 
  \multicolumn{2}{c}{} & 
  \multicolumn{1}{c}{$\rm [{\mu}as/yr]$ } & 
  \multicolumn{1}{c}{$[v_{\rm app}/{\rm c} ]$} \\ 
	\cline{1-4} 
0016+731 & {\rm UC}  &  $ 32 \pm  31$    &   $1.9 \pm 1.8$  \\ 
0153+744 & {\rm UA2} &   $71 \pm   6$    &   $4.7 \pm 0.4$  \\ 
0454+844 & {\rm UB}  & $-100 \pm   3$    &   $-5.1 \pm 0.2$ \\ 
         & {\rm UC}  & $-217 \pm 140$    &   $-11.0 \pm 7.4$  \\ 
0716+714 & {\rm UB }&  $-105 \pm  100$   & $-1.6 \pm 1.5$  \\
0836+710 & {\rm UA2 }&  $-13 \pm   6$    & $-0.8 \pm 0.4$  \\
	 & {\rm UA3 }&  $118 \pm   7$    &  $7.6 \pm 0.5$  \\
	 & {\rm UB }&  $110 \pm   16$    &  $7.1 \pm 1.0$  \\
	 & {\rm UC }&  $101 \pm   16$    &  $6.5 \pm 1.0$  \\
1749+701 & {\rm UB  }&  $141 \pm   25$   &  $5.1 \pm 0.9$  \\
	 & {\rm UC2 }&  $732 \pm   603$  &  $26.5 \pm  21.8$  \\
	 & {\rm UD  }&  $161 \pm    19$  &   $5.8 \pm 0.7$   \\
	 & {\rm UE2 }&  $-150 \pm   62$  & $-5.4 \pm 2.2$   \\
1803+784 & {\rm UB1  }&  $17 \pm   16$   &  $0.6 \pm 0.5$  \\
	 & {\rm UB2  }&  $133 \pm  24$   &  $4.4 \pm 0.8$  \\
2007+777 & {\rm UA1}  &   $52 \pm   48$  &  $1.0 \pm 1.0$  \\
	 & {\rm UB1}  &   $56 \pm   11$  &  $1.1 \pm 0.2$  \\
	 & {\rm UC }  &  $-88 \pm   61$  &  $-1.8 \pm 1.2$ \\
	 & {\rm UF }  &  $350 \pm   203$ &  $7.0 \pm  4.0$ \\
   \hline
 \end{tabular}}
\medskip
$^\dagger$ Proper motions are listed for components observed at three or more epochs, whose least-squares fit showed a motion larger than 1$\sigma$, which is the quoted uncertainty. See details in the main text  and Fig.~\ref{fig:comp_positions}.
\end{table}