`` `` special features of the research include ( 1 ) a phase-of-life-specific , rather than an age-specific , analysis of mortality , and ( 2 ) the use of measures based upon person-years of life in phase intervals , rather than survival rates or expectation of life at given ages . the empirical results suggest that the mortality decline can be described as a two-stage process : an initial stage of substantial improvement in life expectancy between 1950 and 1965 , and a final stage of slow gain in life expectancy since 1965 . '' ''
C0001779
age
C0680083
stage o