A child born in a Glasgow, Scotland suburb can expect a life 28 years shorter than another living only 13 kilometres away. A girl in Lesotho is likely to live 42 years less than another in Japan. In Sweden, the risk of a woman dying during pregnancy and childbirth is 1 in 17 400; in Afghanistan, the odds are 1 in 8. Biology does not explain any of this. Instead, the differences between - and within - countries result from the social environment where people are born, live, grow, work and age.