The death rate began to fall from about 1870 and continued until 1930. It rose slightly during the 1930s and 1940s - depression and World War 2 - declined since the 1950s.
Criticism of the improved nutrition argument: does not explain why females who receive a smaller share of family food supply lived longer than males, and fails to explain why deaths from some infectious diseases such as measles and infant diarrhoea, actually rose at a time of improving nutrition
The largest decline in death rates has come from the reduction of people smoking. However, in the 21st century obesity has replaced smoking as the new lifestyle epidemic.