James Teufel v. Northern Trust Company

Easterbrook, Circuit Judge.

In 2012 Northern Trust changed its pension plan. Until then it had a defined-benefit plan under which retirement income depended on years worked, times an average of each employee's five highest-earning consecutive years, times a constant. Example: 30 years worked, times an average high-five salary of $50,000, times 0.018, produces a pension of $27,000. (We ignore several wrinkles, including an offset for Social Security benefits, a limit on the number of credited years, and a limit on the maximum credited earnings.) The parties call this the Traditional formula. As…