\begin{tabular}{l ccc c ccc}
\toprule
 & \multicolumn{3}{c}{Random holdout} & & \multicolumn{3}{c}{Forward-in-time holdout} \\
\cmidrule{2-4}\cmidrule{6-8}
Model & MdAPE [95\% CI] & $\Delta$ vs.\ A6 [95\% CI] & $t_{\mathrm{DM}}$ & & MdAPE [95\% CI] & $\Delta$ vs.\ A6 [95\% CI] & $t_{\mathrm{DM}}$ \\
\midrule
\multicolumn{8}{l}{\itshape A. Functional form}\\
\quad A1 Linear & 18.2 [16.9, 19.6] & +0.6 [+0.1, +1.1] & 12.3$^{***}$ &  & 20.4 [19.1, 21.7] & -1.4 [-2.3, -0.4] & 6.3$^{***}$ \\
\quad A2 Semi-log & 19.0 [17.9, 20.2] & +1.4 [+1.1, +1.8] & 10.2$^{***}$ &  & 23.2 [21.7, 24.7] & +1.4 [+0.8, +2.3] & 7.8$^{***}$ \\
\quad A3 Log-log & 18.0 [17.1, 19.0] & +0.4 [+0.3, +0.5] & 4.6$^{***}$ &  & 21.8 [20.5, 23.2] & +0.0 [-0.0, +0.2] & 1.8$^{*}$ \\
\quad A4 Box--Cox & 18.6 [17.5, 19.7] & +0.9 [+0.7, +1.3] & 10.7$^{***}$ &  & 21.0 [19.7, 22.2] & -0.8 [-1.4, -0.1] & 4.3$^{***}$ \\
\quad A5 Quadratics & 19.2 [18.2, 20.2] & +1.5 [+1.1, +2.1] & 5.5$^{***}$ &  & 23.3 [21.9, 24.9] & +1.6 [+1.1, +2.2] & 6.1$^{***}$ \\
\quad A6 Splines & 17.6 [16.7, 18.6] & --- & --- &  & 21.7 [20.5, 23.1] & --- & --- \\
\multicolumn{8}{l}{\itshape B. Time effects}\\
\quad B1 No time FE & 22.0 [21.1, 23.3] & +4.4 [+3.4, +5.6] & 8.2$^{***}$ &  & 29.3 [27.3, 31.5] & +7.6 [+6.0, +9.0] & 5.3$^{***}$ \\
\quad B2 Year FE & 19.1 [18.1, 20.2] & +1.5 [+1.1, +2.2] & 6.1$^{***}$ &  & 23.7 [22.2, 25.3] & +1.9 [+1.3, +2.8] & 6.2$^{***}$ \\
\quad B3 Quarter FE & 19.2 [18.2, 20.2] & +1.5 [+1.1, +2.1] & 5.5$^{***}$ &  & 23.3 [21.9, 24.9] & +1.6 [+1.1, +2.2] & 6.1$^{***}$ \\
\quad B4 Month FE & 19.3 [18.4, 20.4] & +1.7 [+1.2, +2.5] & 5.7$^{***}$ &  & 22.9 [21.5, 24.4] & +1.1 [+0.7, +1.8] & 6.0$^{***}$ \\
\multicolumn{8}{l}{\itshape C. Spatial controls}\\
\quad C1 No spatial FE & 28.8 [27.3, 30.1] & +11.2 [+10.1, +12.3] & 7.7$^{***}$ &  & 29.0 [27.4, 30.3] & +7.3 [+5.0, +9.2] & 11.1$^{***}$ \\
\quad C2 Municipality FE & 19.2 [18.2, 20.2] & +1.5 [+1.1, +2.1] & 5.5$^{***}$ &  & 23.3 [21.9, 24.9] & +1.6 [+1.1, +2.2] & 6.1$^{***}$ \\
\quad C3 Grid 5.5 km & 18.7 [17.8, 20.0] & +1.1 [+0.2, +2.3] & 2.5$^{**}$ &  & 24.3 [22.5, 26.4] & +2.5 [+1.6, +3.5] & 4.5$^{***}$ \\
\quad C4 Grid 1.1 km & 21.0 [20.1, 21.9] & +3.3 [+2.9, +3.8] & 6.8$^{***}$ &  & 25.3 [24.3, 26.3] & +3.6 [+2.1, +4.9] & 12.4$^{***}$ \\
\multicolumn{8}{l}{\itshape D. Estimation method}\\
\quad D1 OLS & 19.3 [18.4, 20.4] & +1.7 [+1.2, +2.5] & 5.7$^{***}$ &  & 22.9 [21.5, 24.4] & +1.1 [+0.7, +1.8] & 6.0$^{***}$ \\
\quad D2 Ridge & 17.7 [16.8, 18.7] & +0.1 [-0.0, +0.2] & 2.6$^{***}$ &  & 22.3 [21.0, 23.7] & +0.5 [+0.5, +0.6] & 6.6$^{***}$ \\
\quad D3 Random forest & 14.6 [13.7, 16.2] & -3.0 [-4.6, -1.5] & -2.9$^{***}$ &  & 21.3 [19.9, 23.0] & -0.4 [-1.5, +0.6] & -1.6 \\
\quad D4 Boosting & 14.4 [13.7, 15.7] & -3.2 [-4.7, -1.9] & -3.6$^{***}$ &  & 21.2 [19.7, 22.9] & -0.5 [-1.7, +0.6] & -1.6 \\
\quad D5 Boosting, no coord. & 23.2 [22.1, 25.1] & +5.6 [+3.9, +7.5] & 4.5$^{***}$ &  & 26.2 [25.2, 27.5] & +4.5 [+2.9, +6.2] & 5.9$^{***}$ \\
\quad D6 $k$-NN comparables & 21.2 [19.4, 23.5] & +3.6 [+1.0, +5.9] & 4.8$^{***}$ &  & 25.6 [23.1, 28.3] & +3.9 [+1.8, +5.6] & 4.0$^{***}$ \\
\bottomrule
\end{tabular}