  The issue of longevity has been long time recognized as one of key concepts
in demography. A particular aspect of longevity addressed in this paper is the
difference in average observed duration of life for female and male population,
called observed lifespan differential. Using the data from Human Mortality
Database, the dynamics of the observed lifespan differential is studied for a
large number of countries worldwide from 1960 to 2014. An interesting
phenomenon that the growing trend of the observed lifespan differential at the
beginning of the studied interval does not persist, i.e. that it reverts to
stagnation or even decline is revealed for a large majority of countries in the
dataset. In a number of case studies, a strong association of lifespan dynamic
with disruptive events such as wars, dissolutions or integrations of states or
policy measures is demonstrated. Finally, a novel method of calculating the
observed lifespan differential of a population from mortality indicators of its
subpopulations is introduced and applied to the analysis of the observed
lifespan differential in Israel from 1990 to 2000.
