Actions taken in response to goals set by the United Nations have reduced the deaths of children younger than five from 93 per 1,000 live births in 1990 to 39 in 2018. Low- and middle-income countries, which generally have higher under-5 mortality rates (U5MR) than their richer counterparts, have achieved some of the largest decreases. A recent paper in Nature suggests there is more to the story, however. Researchers who studied local U5MR rates in districts, counties, states and provinces within 99 low- and middle-income nations from 2000 to 2017 found great variability within many countries—especially those with particularly high or low rates overall. In some cases, though, subnational gaps have narrowed substantially. One important insight: in some countries, the ratio of infant (younger than one) deaths to under-5 deaths has risen, suggesting that preventing fatalities among the youngest children may be tougher to attain.