Ind. Code § 10-12-5-4

Sec. 4. As an incentive to all employees of the department, the supplemental pension benefits of this chapter shall be increased by more than the increase provided in section 3(c) or 3(d) of this chapter, at the rate of a five percent (5%) per year increase for each year of active service over twenty (20) years up to thirty (30) years of service, as calculated in section 3(c) or 3(d) of this chapter.