The 20th century has seen numerous improvements in health and the result is a much larger population. But exactly how much larger is the population because of these changes in health? In an article in the September 1996 Population and Development Review, Kevin M. White and Samuel H. Preston underscore just how significant the change has been by looking at what the population of the United States would be if death rates in 1900 had remained stable.
White and Preston offer four scenarios of population size in 2000. The actual estimated population in the U.S. in 2000 is 276 million persons. If, on the other hand, death rates at all ages had been fixed at 1900 levels, the population in 2000 would only have been 139 million people.
Most of the difference is accounted for by reducing childhood death. When death rates for 0-14 are fixed at 1900 levels but death rates for other age groups vary at actual rates, the population jumps to 186 million.
When death rates for ages 15-49 are fixed at 1900 levels, the population jumps to 225 million, and when death rates for ages 50+ are fixed at 1900 levels the population jumps to 258 million.
Although decreasing infant mortality and early childhood death have been of overwhelming importance, the population would still be only half of what it is today had it not been in improvements in mortality rates for those aged 15 and over.