AngloGold Ashanti (AU) had the highest return in December 2018 by a large-cap US stock, returning 23%.

ASSET	MONTH	% RETURN
AngloGold Ashanti (AU)	December 2018	23.04%
Wheaton Precious Metals (WPM)	December 2018	22.06%
First Majestic Silver (AG)	December 2018	18.99%
Gold Fields Ltd ADR (GFI)	December 2018	17.73%
Harmony Gold Mining (HMY)	December 2018	16.99%
Kinross Gold (KGC)	December 2018	16.13%
Royal Gold (RGLD)	December 2018	15.68%
Lattice Semiconductor (LSCC)	December 2018	15.53%
Grupo Aeroportuario del Pacifico SAB De CV ADR (PAC)	December 2018	15.31%
IAMGold (IAG)	December 2018	14.29%
Agnico Eagle Mines (AEM)	December 2018	12.91%
Korea Electric Power Corp ADR (KEP)	December 2018	10.24%
Sibanye Gold Ltd ADR (SBSW)	December 2018	10.11%
Pan American Silver (PAAS)	December 2018	10.11%
Coeur Mining (CDE)	December 2018	9.56%
Alamos Gold (AGI)	December 2018	8.43%
Companhia de Saneamento Basico do Estado de Sao Paulo SABESP ADR (SBS)	December 2018	8.18%
Genmab A-S (GMAB)	December 2018	6.77%
Palo Alto Networks (PANW)	December 2018	6.6%
Equinox Gold (EQX)	December 2018	6.57%
Newmont Goldcorp (NEM)	December 2018	6.09%
Broadcom (AVGO)	December 2018	4.8%
America Movil SAB de CV ADR (AMX)	December 2018	4.01%
Edison International (EIX)	December 2018	3.87%
Kratos Defense & Security Solutions (KTOS)	December 2018	3.45%

Large-cap stocks are treated as having a market cap of $10B+.