Source: Katherine G. Carman, Christine Eibner and Susan M. Paddock, Health Affairs, published ahead of print May 6, 2015
From the abstract:
We examined insurance transitions between September 2013 and February 2015, before and after the Affordable Care Act’s coverage-related provisions took effect in 2014. We found that 22.8 million people gained coverage and that 5.9 million people lost coverage, for a net increase of 16.9 million people with insurance.
RAND press release