Poorer people, on average, live shorter lives. This pattern can be seen even in wealthy countries with extensive welfare systems. In Norway, for example, 40-year-old men in the richest 1% could expect to live almost 14 years longer than those in the poorest 1%. In the US, the equivalent gap is nearly 15 years. A 2025 World Health Organization report warned that international targets for reducing health inequalities by 2040 are likely to be missed.
Efforts to explain these gaps have often focused on people’s circumstances in adulthood, including their income and working conditions. Increasingly, though, researchers have looked further back, to the conditions in which people grow up.
