Health insurers outside the Blue Cross and Blue Shield system have relied heavily on Medicaid business to make up for falling commercial plan enrollment in the past 18 months.

Analysts at Mark Farrah Associates have publishing data on the shift in a commentary based on reviews of insurer reports filed since major Patient Protection and Affordable Care Act (PPACA) medical insurance market changes took effect in January 2014.

The newest enrollment reports in the analysis were for the period ending June 30, 2015.

Because the PPACA public exchange system had such a rocky start in early 2014, and because the PPACA exchange plan enrollment system is seasonal, comparing the mid-2015 data with the mid-2014 data may provide the first meaningful indication of how enrollment is changing over time now that the new rules are in effect.

Total enrollment increased 0.5 percent at Blue Cross and Blue Shield plans between June 2014 and June 2015, to 105 million.

At non-Blue plans total enrollment increased 5 percent, to 150 million, according to the Mark Farrah analysts. 

At the Blues, enrollment in commercial plans, including commercial plans sold through the PPACA public exchange system, fell 0.1 percent, to 93 million. Enrollment in Medicare plans increased 1 percent, to 2.8 million, and enrollment in Medicaid plans increased 6.7 percent, to 9.1 million.

The picture looked different at the non-Blues.

There, commercial plan enrollment fell 1.4 percent, to 102 million. Medicare enrollment rose 12 percent, to 13 million, and Medicaid enrollment climbed 26 percent, to 35 million.