The nation's uninsured rate has plunged to a new low as more consumers shop in Obamacare's exchanges, according to the latest Gallup statistics.

The uninsured rate among adults is now 12.9 percent, down from 13.4 percent in the third quarter of 2014 and down significantly from 17.1 percent a year ago, the new poll released Tuesday finds, marking a drop of 5 percent since the individual mandate under the Patient Protection and Affordable Care Act went into effect.

Though the uninsured rate has declined across nearly all key demographic groups in year one of PPACA, the sharpest decline in the uninsured has been among African-American and low-income Americans. Among Hispanics — the largest population of the nation's uninsured — the rate has dropped nearly 7 percent, but still remains high at 32.4 percent. And, pollsters note, across age groups, the uninsured rate dropped the most among 18- to 25-year-olds, falling about 6 points from a year ago.