Michigan Compiled Laws, Chapter 500. Insurance Code of 1956 § 500.3705

(a) For a health maintenance organization, only industry, age, and group size may be used for determining the premiums within a geographic area for a small employer located in the geographic area. For a commercial carrier, only industry, age, group size, and health status may be used for determining the premiums within a geographic area for a small employer located in the geographic area.

(b) For a health benefit plan delivered, issued for delivery, or renewed in this state on or after January 1, 2014, the premiums charged during a rating period to small employers must be determined only by using the rating factors set forth in section 3474a.  1

(c) The premiums charged during a rating period by a health maintenance organization or commercial carrier for a health benefit plan in a geographic area to small employers located in the geographic area must not vary from the index rate for the health benefit plan by more than 45% of the index rate.

(d) Except as otherwise provided in this section, the percentage increase in the premiums charged to a small employer in a geographic area for a new rating period must not exceed the sum of the annual percentage adjustment in the geographic area's index rate for the health benefit plan and an adjustment under subdivision (a). The adjustment under subdivision (a) must not exceed 15% annually and must be adjusted pro rata for rating periods of less than 1 year. This subdivision does not prohibit an adjustment because of change in coverage.