Mortality has fallen for almost everyone. You would expect this: health care and lifestyles (most notably, smoking rates) have improved. Less predictably, age affects how those gains are divvied out between rich and poor (see chart). Those over 50 have done best in rich counties, reinforcing the notion that the link between income and health is strengthening for the middle-aged. Yet among the young--and particularly among young men--the biggest gains have been in the poorest places.

There are three likely explanations. First, crime has fallen, benefiting poor areas more. In 1990 there were 37 homicides per 100,000 men aged 18-24. By 2014 there were 20. This has particularly affected black men, who more frequently fall victim to murder. In 1990 twice as many young black men died from any cause as young white men. That has fallen to 50% more, with the lower murder rate accounting for four-fifths of the improvement.

Second, HIV is killing fewer people. This is partly due to fewer cases. In 1990 there were 21 incidences of HIV/AIDS per 100,000 men; today there are 12 (though all the progress was before 2000). It is also due to better treatment. Because the HIV epidemic is concentrated in poor, black, southern areas, falling deaths from HIV make mortality rates more equal. HIV mortality has fallen most among 25- to 44-year-olds; among black men in this age-group, HIV deaths are down by 90% since 1990.

The third explanation is better health care for mothers, babies and children. During the 1980s, for instance, Medicaid coverage for pregnant women was greatly expanded. The benefits were long-lasting: a study in 2015 found those whose mothers were included in the expansion were healthier in adulthood. Among other things, they were less likely to be obese.

In 1997 the federal government also began helping states provide health insurance to children in families that were poor, but not poor enough to qualify for Medicaid. This has probably reduced infant deaths that happen after mothers and babies leave hospital. A study in 2014 found that such deaths are largely responsible for America's persistently high infant-mortality rate compared with Europe's.

Targeted interventions such as the 1997 reform probably reduced infant mortality among the poor. The expansion of the earned-income tax credit in the 1990s may have helped, too, by reducing the strain on mothers, or improving toddlers' nutrition. Other public-health improvements, such as cleaner air--particularly important for childhood health--have also disproportionately benefited poor areas.

These trends are especially welcome because more equal mortality should persist throughout the lives of today's youngsters, argues Ms Currie.