Final answer:
The percentage of Americans with health insurance increased substantially in 2014 due to the implementation of the Affordable Care Act. This law helped to make healthcare more affordable and accessible, resulting in approximately 20 million Americans gaining health insurance coverage. The uninsured rate dropped from 20.3% in 2012 to 11.5% by 2016.
Step-by-step explanation:
The year in which the percentage of Americans with health insurance increased substantially was 2014. This significant increase can be attributed to the Affordable Care Act (ACA), which came into full force that year. The ACA, also known as Obamacare, introduced several measures to increase healthcare affordability, expand insurance coverage, and lower the number of uninsured Americans. Prior to the ACA's full implementation, healthcare costs were rising at more than double the rate of inflation, and a significant portion of the U.S. population remained uninsured, with 32 million non-elderly adults without insurance in 2015.
The effects of the ACA were substantial in reducing the uninsured rate. By 2016, the percentage of those without insurance in the US had fallen from 20.3% in 2012 to 11.5%. This dramatic drop represented approximately 20 million Americans gaining coverage under the ACA. After the implementation of the ACA, the share of the population without health insurance continued to decline, reaching as low as 8.6% according to Census data from 2020.
Healthcare insurance was made more accessible not only through the establishment of health insurance marketplaces but also by expanding Medicaid eligibility in some states and by mandating that people with preexisting conditions could no longer be denied coverage. These factors collectively led to the substantial increase in insured Americans in 2014, making healthcare more accessible and reducing the financial burdens associated with medical care for many families.