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Just as we can use a small, contained population to understand facts about fertility, we can do the same to understand facts about migration. Let’s 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 fertility rate is 2.0 (2,000 children divided by 1,000 women) and its population is 4,000. |
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MIGRATION PRIMER
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 fertility rate remains 2.0 and its population remains stable at 6,000.
Imagine each year, 30 children, half girls, half boys, migrate to this island. Thirty migrants 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 migrants have come to the island and produced 1,830 children and 930 grandchildren. Together, they have nearly doubled the otherwise stable population of the island to 11,460. Of course, if the birth rate of these migrants is greater than the replacement fertility rate of 2.0, growth of the island’s population will be even greater.
Even with a seemingly low migration rate of 0.5%--America’s approximate net migration rate--and even when migrants have low fertility rates--often not true of migrants to America--the result can be a near doubling of population in three generations. We should welcome migrants to the U.S., but we should also remember the numbers. If we do not want America’s population to grow from 300 million to 600 million or to one billion, we should reduce migration far below its current level.
Think about migration. Think about an America of 600 million or one billion! |
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©2006 Edward C. Hartman. All Rights Reserved
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