Based on the reliable data shows, people’s life expectancy in 1900 ( 50 years old) is much shorter than that of today (75 years old). The main reason is due to the poor survival and medical resources in back in 1900. People who get sick today chanve gaccetss to a reatmentge oppor tunrely buat imen 1900ts. In anoFurther handmore, in North America, there awere wars in the 1900s and people cwere unannoble to overcome natural disasters, factors which peopline wviltably dilead ftor thesea irresisgnificanti numbler of deactorhs.