Strategy. Principal Investment Strategies Under normal circumstances, the Fund invests at least 80% (and, typically, substantially all) of its net assets (plus the amount of any borrowings for investment purposes) in the equity securities of companies included in the S&P MidCap 400 Index (Index), in weightings that approximate the relative composition of the securities contained in the Index, and in S&P MidCap 400 Index futures contracts. The Index is a widely recognized, unmanaged index representative of common stocks of mid-capitalized U.S. companies. The companies chosen for inclusion in the Index tend to be industry leaders within the U.S. economy as determined by Standard & Poors . However, companies are not selected by Standard & Poors for inclusion in the Index because … Show more… Principal Investment Strategies Under normal circumstances, the Fund invests at least 80% (and, typically, substantially all) of its net assets (plus the amount of any borrowings for investment purposes) in the equity securities of companies included in the S&P MidCap 400 Index (Index), in weightings that approximate the relative composition of the securities contained in the Index, and in S&P MidCap 400 Index futures contracts. The Index is a widely recognized, unmanaged index representative of common stocks of mid-capitalized U.S. companies. The companies chosen for inclusion in the Index tend to be industry leaders within the U.S. economy as determined by Standard & Poors . However, companies are not selected by Standard & Poors for inclusion in the Index because they are expected to have superior stock price performance relative to the market in general or other stocks in particular. As of December 31, 2021, the market capitalization range of companies included in the Index was $1.74 billion to $18.58 billion. If the securities represented in the Index were to become concentrated in any particular industry, the Funds investments would likewise be concentrated in securities of issuers in that industry; the Index is not currently concentrated in any single industry. The Fund is passively managed, which means it tries to replicate the investment composition and performance of the Index by using computer programs and statistical procedures. The Funds subadviser, Northern Trust Investments, Inc. (NTI), will buy and sell securities in response to changes in the Index. The Fund may use Index futures contracts, a type of derivative, to gain exposure to the Index in lieu of investing in cash, or to reduce its exposure to the Index while it sells the securities in its portfolio. Use of Index futures contracts by the Fund may create investment leverage. Because the Fund, unlike the Index, is subject to fees and transaction expenses, the Funds returns are likely to be less than those of the Index. NTI expects that, under normal circumstances, the annual performance of the Fund, before fees and expenses, will track the performance of the Index within a 0.95 correlation coefficient. Show less