in the years from to only a few countries had a level of life expectancy greater than years and only per cent of the world s population lived in such countries at that time per cent of the world s population lived in countries where the life expectancy at birth was less than years figure the reductions of mortality since the middle of the twentieth century have been so substantial that the proportion of the population living in countries with a life expectancy below years had decreased to only per cent for the period between and