The supplemental poverty measure, which takes into account additional living expenses not factored into the official poverty formula, also indicates the percentage of impoverished Americans age 65 and older grew the most and the portion of Hispanics in poverty for the first time surpassed that of African-Americans.
The percentage of poor Americans 65 and older increased to 15.9 percent -- essentially equal to the 16 percent national average -- from the official 9 percent figure for elderly Americans, the Census Bureau said.
The official figures were released in September. The new figures are "intended to better reflect contemporary social and economic realities," the bureau said.
The increase among the elderly was largely due to rising medical expenses such as Medicare insurance premiums, deductibles and prescription-drug costs not counted in the official rate, the bureau said.
The share of poor Hispanics increased to 28.2 percent from the official 26.7 percentage while the portion of poor blacks dropped to 25.4 percent from 27.5 percent, the bureau said.
The Hispanic increase was due in part to low participation among non-English-speaking Hispanic immigrants in government-aid programs such as housing assistance and the Supplemental Nutrition Assistance Program, commonly known as food stamps.
The supplemental poverty measure does not replace the bureau's official poverty formula, which will still determine eligibility and distribution of federal aid to people who are poor, the bureau said.
Poverty for Asians increased to 16.7 percent from 12.1 percent under the official measure. The rate among non-Hispanic whites rose to 11.1 percent from 10 percent.
The percentage of poor working-age adults ages 18-64 grew to 15.2 percent from 13.7 percent, due in large part to commuting and childcare costs, the bureau said.
The poverty rate for children dropped to 18.2 percent from 22 percent.
Under the supplemental formula, the West, including Alaska and Hawaii, had the greatest share of people in poverty, at 19.4 percent -- nearly 1 in 5 -- up from the official 15.4 percent.
The South was next, at 16.3 percent, down from 17 percent; the Northeast followed, at 14.5 percent, up from 12.9 percent, and the Midwest had the smallest portion, at 13.1 percent, down from 14 percent.