Patrick Industries (PATK) had the highest return between 2011 and 2012 by a mid-cap US stock, returning 674.1%.

ASSET	YEARS	% RETURN
Patrick Industries (PATK)	2011-2012	674.14%
ACADIA Pharmaceuticals (ACAD)	2011-2012	290.76%
Travere Therapeutics (TVTX)	2011-2012	272.22%
Acadia Healthcare (ACHC)	2011-2012	243.38%
Silicon Motion Technology (SIMO)	2011-2012	227.65%
CVR Energy (CVI)	2011-2012	216.61%
Vipshop (VIPS)	2011-2012	197.32%
Sandstorm Gold Ltd N (SAND)	2011-2012	191.36%
HCI (HCI)	2011-2012	185.88%
Generac (GNRC)	2011-2012	179.73%
Jazz Pharmaceuticals (JAZZ)	2011-2012	167.86%
Lithia Motors (LAD)	2011-2012	166.24%
Golar LNG (GLNG)	2011-2012	165.06%
HF Sinclair (DINO)	2011-2012	158.24%
Melco Resorts & Entertainment (MLCO)	2011-2012	156.71%
Fortune Brands Innovations (FBIN)	2011-2012	145.55%
Six Flags Entertainment (FUN)	2011-2012	141.5%
CommVault Systems (CVLT)	2011-2012	141.46%
NewMarket (NEU)	2011-2012	138.38%
SPS Commerce (SPSC)	2011-2012	133.23%
Dillard's (DDS)	2011-2012	132.46%
Ligand Pharmaceuticals (LGND)	2011-2012	131.21%
Polaris Industries (PII)	2011-2012	121.47%
Grupo Aeroportuario del Sureste SAB de CV ADR (ASR)	2011-2012	117.45%
IPG Photonics (IPGP)	2011-2012	111.54%

Mid-cap stocks are treated as having a market cap between $2B and $10B.