 Alliancebernstein L.P. grew its position in shares of iShares Russell Mid-Cap ETF NYSEARCA:IWR by 1.2 in the fourth quarter, according to its most recent 13F filing with the Securities and Exchange Commission SEC. The institutional investor owned 20,840 shares of the companys stock after purchasing an additional 237 shares during the period. Alliancebernstein L.P.s holdings ... 