The analysis, based on claims from 21 Blue Cross and Blue Shield insurers around the country, highlights a challenge the companies say they face covering the population that signed up for plans issued under the ACA, sold both on the law’s signature marketplaces and outside them.

A number of Blue Cross and Blue Shield insurers faced increasing financial losses in 2015 on their ACA business, and some have responded by raising rates or tweaking their approaches this year.

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