Harmony Gold Mining (HMY) had the highest return in January 2015 by a large-cap US stock, returning 63.2%.

ASSET	MONTH	% RETURN
Harmony Gold Mining (HMY)	January 2015	63.16%
Neurocrine Biosciences (NBIX)	January 2015	49%
Halozyme Therapeutics (HALO)	January 2015	46.16%
AngloGold Ashanti (AU)	January 2015	45.13%
Agnico Eagle Mines (AEM)	January 2015	38.42%
Newmont Goldcorp (NEM)	January 2015	34.85%
Gold Fields Ltd ADR (GFI)	January 2015	33.18%
Pan American Silver (PAAS)	January 2015	28.84%
Netflix (NFLX)	January 2015	28.41%
Exelixis (EXEL)	January 2015	27.21%
First Majestic Silver (AG)	January 2015	27.11%
Coeur Mining (CDE)	January 2015	25.5%
Coherent (COHR)	January 2015	24.93%
Kinross Gold (KGC)	January 2015	22.83%
Repligen (RGEN)	January 2015	22.49%
Takeda Pharmaceutical Co Ltd ADR (TAK)	January 2015	21.01%
Hecla Mining (HL)	January 2015	19.64%
Franco-Nevada (FNV)	January 2015	19.45%
Lululemon Athletica (LULU)	January 2015	18.26%
Royal Gold (RGLD)	January 2015	17.74%
Wheaton Precious Metals (WPM)	January 2015	14.91%
Diamondback Energy (FANG)	January 2015	14.89%
Encompass Health (EHC)	January 2015	14.46%
Stellantis (STLA)	January 2015	13.98%
Sony (SONY)	January 2015	13.77%

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