\begin{tabular}{c|c|ccc|ccc}
	 & \begin{tabular}{c}Average\\ number of firms\end{tabular} &
	\begin{tabular}{c}Consumer\\ surplus\end{tabular} &
	\begin{tabular}{c}Producer\\ surplus\end{tabular} &
	\begin{tabular}{c}Total\\ surplus\end{tabular} &
	 C1 & C4 & HHI\\\hline\hline
