To pursue its goal, the fund generally is fully invested in stocks included in the S&P MidCap 400® Index and in futures whose performance is tied to the index. It generally invests in all 400 stocks in the S&P MidCap 400® Index in proportion to their weighting in the index. The S&P MidCap 400® Index is an unmanaged index of 400 common stocks of medium-size companies.