The life expectancy gap between America's rich and poor is shrinking for the young, a new study reports.

In fact, life expectancy at birth has been improving for virtually all income groups born in 1990 onward. The results reveal that many of the U.S. policies directed at improving the health of the young and the poor may have been successful. Previous research suggests that disparities in mortality inequality have widened since the start of the 21st century - with Americans in the top income bracket gaining several years of life expectancy while those at the bottom have gained almost nothing, or even experienced a life expectancy decline.

Critically, however, much of this work was based on studies that calculate life expectancy at age 40 or age 50, ignoring improvements that have been occurring at younger ages (and that have been shown to be important predictors of a cohort's health and mortality later in life). Here, to provide what they believe is a more accurate picture, Janet Currie and colleagues look at the life expectancy of people from birth.

They studied inequality in mortality for all age groups in 1990, 2000, and 2010 in an analysis based on counties ranked by poverty levels. They found that while mortality inequality at older ages has been increasing (consistent with results from previous studies), mortality inequality for poor children up through poor adults age 20 has actually been on rapid decline. These mortality improvements were most pronounced in poorer counties, the researchers say, implying a strong decrease in mortality inequality.

Since these younger groups will form the future adult U.S. population, this research suggests that inequality in old age mortality is likely to decline going forward.