Source: Lipper Analytical Services and Morningstar, Inc.

Past performance is no guarantee of future results. Northern Institutional ratings/rankings are for Class A only (Shares class for money market funds); other classes may vary. Ratings/rankings reflect fee waivers in effect; in their absence, ratings/rankings may have been lower. Ratings/rankings are subject to change monthly.

Star ratings are based on a Morningstar Risk-Adjusted Return measure that accounts for variation in a fund's monthly performance (including the effects of sales charges, and redemption fees), placing more emphasis on downward variations and rewarding consistent performance. The overall rating is a weighted average of the 3-, 5-, and 10-year (if applicable) returns. 5 stars = top 10% of funds in an asset category; 4 stars = next 22.5% of funds; 3 stars = next 35%. A fund must be in existence three years to be rated.

3-year ratings: Each of the funds in the table received 4 stars except the U.S. Treasury Index Portfolio, which received 5 stars. 5-year ratings: Each of the funds in the table received 4 stars except the U.S. Treasury Index Portfolio, which received 5 stars. 10-year ratings: Each of the funds in the table received 4 stars except the Small Cap Value Fund, which received 3 stars and the U.S. Treasury Index Portfolio, which received 5 stars.

For the 3-year period, the number of funds in each category is the same as shown above for the overall ratings. For the 5- and 10-year period, the number of funds in each rating category was as follows, respectively: small value = 261 and 98, intermediate-term bond = 830 and 433, short government = 131 and 102, intermediate government = 340 and 222 and muni national long = 248 and 197.

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Funds are classified by investment objectives defined by Lipper Analytical Services and ranked by total return. 3-, 5- and 10-year rankings (if applicable) as of 3/31/08: Equity Index Portfolio, 30 out of 171, 26 out of 154 and 21 out of 80; Tax-Exempt Portfolio, 48 out of 218, 60 out of 212, and 20 out of 147; Short Bond Portfolio, 35 out of 210, 41 out of 162 and 17 out of 84; Mid Cap Growth Portfolio, 244 out of 503 and 268 out of 414; Focused Growth Fund, 207 out of 615, 360 out of 521 and 118 out of 247; U.S. Government Securities Portfolio, 10 out of 50, 10 out of 44 and 11 out of 37; Municipal Portfolio, 23 out of 113 and 20 out of 93; Small Cap Value Fund, 70 out of 240, 55 out of 186 and 38 out of 83; and Core Bond Portfolio, 137 out of 466 and 161 out of 395.