Over the past few months, there has been intense focus on the number of sign-ups in the new health insurance marketplaces established under the Affordable Care Act (ACA).¹ But marketplace enrollment is only a small piece of the puzzle: The ACA seeks to achieve nearly universal health insurance coverage using all sectors of the health insurance market. First, the law makes coverage more affordable for people with low and moderate incomes by providing health insurance subsidies for individuals lacking affordable employer insurance and by encouraging states to expand their Medicaid programs. Second, the law makes coverage more accessible to those...