America's most vulnerable residents have made the biggest gains under Obamacare
Nearly one-third of the newly insured adults were Hispanic, and coverage rates soared for low-wage workers such as cooks, hairdressers, and cashiers.
Immigrants - including more than one million non-citizen residents - saw the largest surge in coverage rates, the Times reported.
The health care law's effectiveness has typically been measured by the amount of newly insured people, which was last tallied at 20 million as of February 2016.
The Times analysis, which examined 2014 census data, determined the demographic breakdown of the newly insured.
"The law has clearly reduced broad measures of inequality," Harvard economics professor David Cutler, who was an adviser to President Obama during the 2008 campaign, told the Times. "These are people who blend into the background of the economy. They are cleaning your hotel room, making your sandwich. The law has helped this population enormously.
Two-thirds of the country's newly insured adults were minorities. Of the 1.2 million non-citizens who gained coverage, 60 percent were Hispanic and around one-third were Asian. The law also helped cover high rates of part-time workers and residents with only a high school education.
The Times' findings are significant given the context of 2016's election, as both parties vie for Hispanic and minority votes. The health care law - which passed in 2010 without the help of Republicans and was later upheld by the Supreme Court in 2012 and 2015 - remains a hotly disputed piece of legislation which each of the Republican presidential candidates have promised to repeal.
The law still has hurdles to clear. Some Americans still cannot afford coverage, and the Pew Research Center's Mark Hugo Lopez told the Times that the vast majority of the country's 11 million undocumented immigrants remain uninsured.
Furthermore, 19 states have refused to expand their Medicaid programs to cover the poor, as per the Supreme Court's 2012 ruling. This disproportionately affected the coverage rates of black residents, the majority of whom live in those states that have refused the expansion, according to the Pew Charitable Trusts.