Vulcan Materials (VMC) had the best day in December 2011 by a US stock in the S&P 500 (GSPC) on December 12, 2011, returning 17.2%.

ASSET	DATE	% RETURN
Vulcan Materials (VMC)	12/12/2011	17.24%
Akamai Technologies (AKAM)	12/22/2011	15.02%
Lululemon Athletica (LULU)	12/1/2011	12.47%
Caesars Entertainment (CZR)	12/2/2011	12.35%
Micron Technology (MU)	12/22/2011	12.26%
Caesars Entertainment (CZR)	12/13/2011	9.61%
Builders FirstSource (BLDR)	12/2/2011	8.97%
Caesars Entertainment (CZR)	12/1/2011	8.55%
DexCom (DXCM)	12/29/2011	8.17%
Masco (MAS)	12/29/2011	7.97%
Netflix (NFLX)	12/12/2011	7.92%
Micron Technology (MU)	12/7/2011	7.83%
Super Micro Computer (SMCI)	12/9/2011	7.71%
Caesars Entertainment (CZR)	12/9/2011	7.65%
Cooper Companies (COO)	12/9/2011	6.8%
NXP Semiconductors (NXPI)	12/22/2011	6.76%
PulteGroup (PHM)	12/20/2011	6.75%
ON Semiconductor (ON)	12/1/2011	6.66%
Advanced Micro Devices (AMD)	12/22/2011	6.45%
Masco (MAS)	12/20/2011	6.28%
Caesars Entertainment (CZR)	12/30/2011	6.25%
Builders FirstSource (BLDR)	12/21/2011	6.22%
Walgreens Boots Alliance (WBA)	12/21/2011	6.21%
Leidos (LDOS)	12/7/2011	6.15%
Incyte (INCY)	12/12/2011	6.08%