The Assessor is required by State Statute to assess your property at one-third of it's fair market value. If he doesn't, DuPage County or the State of Illinois will.
Your tax rate is determined by the taxing bodies you support, ie: school district, fire protection, libraries, hospitals, township, forest preserve, health department, water commission, airport authority, sanitary districts, special police & highway districts.
To reduce your taxes attend their meetings; see how your tax dollars are being spent! And make your feelings known.