During the transition from high fertility and rapid population growth to lower fertility and
slower growth, the working-age population expands relative to the dependent (younger and older)
population, opening a window of opportunity for economic growth. Indeed, when fertility declines
and young-age dependency ratios quickly follow suit , the ratio of working-age people to dependent
people rises as the young population increases more slowly than the working-age population. This
window opens as the number of younger children decreases but closes again as the number of
older people rises. Most Western countries are moving into the later stage of their transition to low
fertility and may not benefit from the demographic bonus as the number of older people is already
very large. On the contrary, some Asian countries are entering and/or are only in the middle of the
transitional period. This paper aims to illustrate the change in demographic window taking into
consideration of different age demarcations to calculate total dependency ratio for Italy, France,
Japan, Singapore and Hong Kong from 1950 to 2050. The results show only when the last age of
the working-age population postponed from the age of 64 to 69 years can significantly lengthen
the duration of demographic window. This favourable condition at least lasts until 2030 and after
that total dependency ratio will gradually rise in Italy and France. The demographic window will
increase by 15 years from 2007 to 2022 in Japan, by 8 years from 2026 to 2034 in Singapore and
by 11 years from 2027 to 2038 in Hong Kong. However, this scenario is less probable because
most people retire earlier than the age of 65 years. Young people also enter a job market later than
the folks before. More discussions are made in the paper