Under-five mortality (the probability of dying between birth and age five) has much bearing on a country’s life expectancy. In places where child mortality rates are very high, life expectancy is dragged down dramatically from what it would be if measured for survivors of early childhood.
For example, in the least developed countries, life expectancy at birth is 62 years. For those who make it to the age of five, life expectancy increases to 68 years. The difference in life expectancy at birth and at age five in the more developed countries is negligible because child mortality rates are so low.
Fortunately, child mortality rates are declining everywhere, and this is happening most rapidly in the least developed countries. Since the late 1960s, the life expectancy at birth has risen by 44% in the least developed countries. The life expectancy at birth has only risen 11% in the most developed countries because it was already high in the late 1960s.
There is still plenty of improvement to be made, however, as 86 out of every 1,000 children under five die in the least developed countries (compared to 6 in the more developed countries).