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Imagine a remote--and unique--island populated by 2,000 children,
half girls,
half boys. As they grow older they pair and have children.
By age 30 they
have had 2,000 children--half girls, half boys--and have no
more. The
island's birth rate is 2.0 (2,000 children
divided by 1,000 women) and its
population is 4,000.
Imagine the second generation of 2,000 children pair and have
children. By age 30 they have had 2,000 children and have no
more. The island's birth rate remains 2.0 and its population
remains stable at 6,000. (Click on "Facts--Birth &
Fertility Rates" for a further explanation of stabilizing
birth rates.)
Imagine each year, 30 children, half girls, half boys, immigrate
to this island. Thirty immigrants represent only 0.5% of the
island's otherwise stable population of 6,000. However, by the
90th year, when the first generation of "natives"
have died, approximately 2,700 immigrants have come to the island
and produced 1,800 children and 900 grandchildren. Together,
they have nearly doubled the otherwise stable population of
the island to 11,400. Of course, if the birth rate of these
immigrants is greater than the replacement rate of 2.0, growth
of the island's population will be even greater.
Even with a seemingly low immigration rate of 0.5%--approximately
the
immigration rate of the U.S.--and even when immigrants have
low birth
rates--often not true of U.S. immigrants--the result can be
a near doubling
of population in three generations. We will welcome immigrants
to the U.S.,
but we should also remember the numbers. If we do not want
U.S. population
to grow from 290 million to 580 million, we will want to reduce
immigration
far below its current level.
Think about immigration. Think about a U.S. of 600 million.
Think Population! |
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