This study looks at the mortality trends of successive cohorts born 1930-1960. We calculated the risk of dying in adulthood using data from the Human Mortality Database and compared 17 western countries. Specifically we focus on male mortality between ages 30-53, although female mortality and other age spans exhibit similar patterns.

We found four distinct patterns for the cohorts born in these year bands:

1. 1930-1938: universal pattern of steadily improving mortality for successive cohorts.
2. 1939-1947: some countries have wide variations between cohorts (Austria, Finland). The Dutch famine of 1945 modestly increased the adult mortality likelihood of children born then. The most significant pattern seen in 11 out of the 17 countries was a sharp improvement for the 1946 cohort compared to those born before and after.
3. 1948-1955: slow or stalling improvements in mortality across cohorts; decline in some countries (USA, Portugal, France, Denmark, Spain).
4. 1956-1960: resumption of mortality improvement trends.

Previous work on Swedish mortality has found that children of lower birth order have a better mortality outlook than higher order children. With the limited data available on births by birth order (only the USA and Switzerland) we found evidence that the proportion of first births to all births may partly explain the trends seen in cohort mortality. During the 1930s fertility declined, and the proportion of first births increased, leading to mortality improvements across successive cohorts. 1946 saw a peak in first births and markedly lower adult mortality for that specific cohort. Subsequent Baby Boom children, however, tended to be (on average) higher order births - and consequently experienced less improvement in their mortality than for earlier cohorts.