The investment seeks investment results that correspond to the investment performance of the S&P MidCap 400® Index. The fund invests primarily in the 400 common stocks included in the S&P MidCap 400® Index to replicate, to the extent practicable and cost effective, the weightings of such stocks in the index. Under normal circumstances, at least 80% of the fund's total assets are invested in securities included in the S&P 400® Index. The components of the index are market capitalization weighted, adjusted for free float, which is the value of shares readily available in the market as held by public investors.