Sony (SONY) had the highest return on May 21, 2013 by a large-cap US stock, returning 8.3%.

ASSET	DATE	% RETURN
Sony (SONY)	5/21/2013	8.27%
Centrais Elétricas Brasileiras SA - Eletrobrás (EBR.B)	5/21/2013	5.86%
Centrais Electricas Brasileiras (EBR)	5/21/2013	4.63%
Merck (MRK)	5/21/2013	4.62%
Cameco (CCJ)	5/21/2013	4.16%
EPAM Systems (EPAM)	5/21/2013	4.13%
YPF Sociedad Anonima (YPF)	5/21/2013	3.75%
AutoZone (AZO)	5/21/2013	3.55%
MakeMyTrip (MMYT)	5/21/2013	3.52%
Deckers Outdoor (DECK)	5/21/2013	3.38%
Royal Bank of Canada (RY)	5/21/2013	2.73%
Carnival (CCL)	5/21/2013	2.7%
CH Robinson Worldwide (CHRW)	5/21/2013	2.64%
Hubbell (HUBB)	5/21/2013	2.64%
Biomarin Pharmaceutical (BMRN)	5/21/2013	2.57%
Vertex Pharmaceuticals (VRTX)	5/21/2013	2.4%
Carnival Plc ADS (CUK)	5/21/2013	2.38%
Biogen (BIIB)	5/21/2013	2.28%
Brookfield Renewable Partners (BEP)	5/21/2013	2.2%
Flex (FLEX)	5/21/2013	2.17%
Descartes Systems (DSGX)	5/21/2013	2.17%
Charter Communications (CHTR)	5/21/2013	1.99%
Old Dominion Freight Line (ODFL)	5/21/2013	1.97%
CBRE Group Inc Class A (CBRE)	5/21/2013	1.95%
Nucor (NUE)	5/21/2013	1.95%

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