The Russell 2000 (INDEXRUSSELL:RUT) is up 2.2% last week, beating out the Russell Midcap (INDEXRUSSELL:RMCC) and S&P 500 (INDEXSP:.INX). Consumer discretionary was the best performing sector for the week, but year-to-date gains are heavily concentrated in biotech, and continued follow through from the RUT will require financials and industrials to start pulling their weight in coming months. Russell 2000 returns are highly concentrated “To make a point as to concentration of return contributions, the top 41 Russell 2000 (INDEXRUSSELL:RUT) stocks on the list have contributed a return equal to the index return,” writes Citi analyst Scott T. Chronert. “Even more telling, of the…