\begin{table}[htbp]\centering\small
\caption{Universe allocation: instruments per asset class $\times$ dollar-volume tercile $\times$ daily-volatility tercile (selection date 2017-12-29; 60 of the 300 instruments are held out)}
\label{tab:universe_strata}
\begin{tabular}{llccc}
\toprule
Asset class & ADV tercile & Vol. low & Vol. mid & Vol. high \\
\midrule
etf & high & 8 & 8 & 8 \\
etf & low & 9 & 8 & 9 \\
etf & mid & 9 & 8 & 8 \\
stock & high & 25 & 25 & 25 \\
stock & low & 25 & 25 & 25 \\
stock & mid & 25 & 25 & 25 \\
\midrule
held out & & \multicolumn{3}{c}{stocks 42, ETFs 18} \\
\bottomrule
\end{tabular}
\end{table}