Global demographic trends are coalescing around an unprecedented milestone in human history: It is estimated that by 2020, people over age 60 will for the first time outnumber children under the age of 5 years old. Global fertility rates have fallen by half over the last half-century from an average of 5 children per woman in 1960 to 2.5 today. In addition, major advances against what were once the world’s top killers—infectious diseases and acute threats to child and maternal health—are allowing more people to live longer than ever before.
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