States' commitment to Medicaid before the Affordable Care Act: trends and implications.

Medicaid insures more than 65 million low-income people, and the Affordable Care Act of 2010 gives states the option to enroll millions more. Historical trends in state Medicaid effort possess important implications for health policy going forward. Nearly all states steadily ratcheted up their Medicaid effort in the period from 1992 to 2009, holding out promise that most will sustain their programs and ultimately participate in the expansion authorized by the Affordable Care Act. But the growth in Medicaid over this period did not appreciably curtail vast geographic disparities in program benefits that threaten to undermine the goals of health reform.