专四晨读美文：Aging Populations

Aging Populations
What is making the world so much older?
There are two long-term causes and a temporary blip
that will continue to show up in the figures
for the next few decades.
The first of the big causes is
that people everywhere are living far longer than they used to,
and this trend started with the industrial revolution
and has been slowly gathering pace.
In 1900 average life expectancy at birth
for the world as a whole was only around 30 years,
and in rich countries under 50.
The figures now are 67 and 78 respectively, and still rising.
For all the talk about the coming old-age crisis,
that is surely something to be grateful for-
especially since older people these days
also seem to remain healthy, fit and active for much longer.
A second, and bigger, cause of the ageing of societies
is that people everywhere are having far fewer children,
so the younger age groups are much too small
to counterbalance the growing number of older people.
This trend emerged later than the one for longer lives,
first in developed countries and now in poor countries too.
In the early 1970s women across the world were still,
on average, having 4.3 children each.
The current global average is 2.6,
and in rich countries only 1.6.
The UN predicts that by 2050 the global figure
will have dropped to just two,
so by mid-century the world's population will begin to level out.
The numbers in some developed countries
have already started shrinking.
Depending on your point of view,
that may or may not be a good thing,
but it will certainly turn the world into a different place.
The temporary blip that has magnified the effects of
lower fertility and greater longevity
is the baby-boom that arrived in most rich countries
after the Second World War.
The timing varied slightly from place to place,
but in America-where the effect was strongest-
it covered roughly the 20 years from 1945,
a period when nearly 80 million Americans were born.
The first of them are now coming up to retirement.
For the next 20 years those baby-boomers
will be swelling the ranks of pensioners,
which will lead to a rapid drop
in the working population all over the rich world.