Final answer:
The Affordable Care Act greatly reduced the number of uninsured Americans from 20.3% in 2012 to 8.6% by 2020, due to expanded Medicaid eligibility and prohibitions on denying coverage to those with preexisting conditions.
Step-by-step explanation:
Since the enactment of the Affordable Care Act (ACA), also known as Obamacare, there has been a significant decrease in the percentage of Americans without health insurance. The U.S. Department of Health and Human Services reports that the rate of uninsured individuals dropped from 20.3% in 2012 to 11.5% in 2016, meaning approximately 20 million Americans gained coverage. This legislation was particularly influential for individuals with preexisting conditions who, prior to the ACA, were often denied coverage. Further reductions occurred, and by 2020, the Census reported that the share of the population without health insurance had further declined to 8.6%.
Key elements contributing to this decline include the expansion of Medicaid eligibility, the establishment of health insurance marketplaces, and provisions ensuring that individuals with preexisting conditions could not be denied coverage. Additionally, the ACA included an individual mandate requiring most Americans to carry health insurance or face a penalty, though this mandate has faced significant political opposition.