Sometime in the Spring of 1996 I telephoned Julian Simon  to run by him the idea that is featured in this June 2002 Freeman column . I was pleased that Julian found the idea to have merit. I cannot now recall why it took me six years to write a column on this idea. The column that I finally wrote is below the fold.
America should re-open its borders to immigrants.
Not until 1924 did the government generally limit the number of people who could come to America and make it their home. If America’s borders had been closed, say, a century earlier, the civilization that we now call “American” would not exist. The Irish, Germans, Italians, Scandinavians, central and eastern Europeans, and many Asians arrived here in bulk during the nineteenth century. Most would have been turned away under the restrictive regime followed since 1924.
When I talk with people about immigration, everyone agrees that the open-borders policy of the eighteenth, nineteenth, and early twentieth centuries was a great boon to America. Without it, we would today be unimaginably poorer and less vibrant. So I then ask: If open borders in the past generated enormous benefits, why not open our borders today? I always get the same answer: “Times change. America had more room and resources then. We could then absorb immigrants better than we can today.”
Room for Immigrants
Since 1820 the years that witnessed the greatest influx of immigrants as a proportion of America’s population were the early and mid-1850s, when annual immigration was about 1.6 percent of the resident population. This figure was approached again in the 1880s and during the first decade of the twentieth century. Today, annual immigration is about 0.25 percent of the resident population—less than one-sixth its level during the first half of the 1850s, and about one-sixth its level during much of the 1880s and the first decade of the twentieth century. (Some people argue that illegal immigrants are undercounted today. Taking the largest estimate I’ve seen of uncounted illegal immigrants, total annual immigrants as a proportion of the U.S. population today would be 1.25 percent of the resident population. While likely overblown, accepting this figure as accurate means that, as a percent of the resident population, immigration today remains well below that of any of the peak years of the past.)
What about our ability to “absorb” these—and even more—immigrants?
An important element of the ability to absorb is living space. Americans today enjoy record levels of residential living space. For example, in 1915, the typical dwelling in America housed 5.63 people; today it houses fewer than half of that number—2.37 people. Combined with the fact that the square-footage of today’s typical dwelling is, on the most conservative estimate, 20 percent greater than it was a century ago, our ability to “absorb” immigrants into our residential living spaces is today more than twice what it was during the era of open borders.
What about land? Contrary to a widely mistaken belief, the amount of land devoted to urban and suburban uses is a tiny percentage of America’s land (even excluding largely unsettled Alaska). While such land use has grown significantly during the past century, today it is at most about 3 percent of the land area of the lower 48 states. (The 3 percent figure is an overestimate because, since about 1960, cities have increasingly incorporated lands that remain largely rural in character but that are classified as “urban.”)
And since at least 1950, the amount of land devoted to public recreation uses and to wildlife refuges has increased faster than has the amount of land devoted to urban and suburban uses. Today, the land area devoted to national and state parks, and to wildlife refuges, is more than seven times greater than it was in 1900. America is nowhere close to being crowded.
Also, we’re much better able to feed ourselves today, even though the amount of land used to grow crops and to pasture animals is no larger now than in 1900. Extraordinary increases in agricultural productivity enable American farmers and ranchers to produce vastly more output on the same amount of land. For example, each acre planted with wheat today produces three times more output than it did a century ago. Similar, and even greater, productivity increases have occurred for nearly all other agricultural products. This productivity explosion is reflected in a much more abundant food supply and lower food prices.
Immigrants, of course, come to America not only to consume but also to work. A measure of our ability to “absorb” workers is capital invested per worker—the amount of machinery and other tools in place for workers to use. Today, the amount of capital invested per worker is more than nine times greater than in 1880 and about 8.5 times greater than in 1924. Because a worker’s productivity rises when he has more capital to work with and his pay is tied closely to his productivity, workers entering the American economy today produce and earn more than workers entering during the open-borders era.
Don’t lose sight of our labor market’s great flexibility. It easily absorbed the massive increase of women workers during the second half of the twentieth century. Over this time, 46 million jobs were created for women, which is more than half of the 80 million jobs created during that same time.
In many other ways, America today is far better able than in the past to absorb more immigrants. For example, compared to 1920, per person today we:
- have greater than ten times more miles of paved roads;
- have more than twice as many physicians;
- have 50 percent more dentists;
- have almost three times as many teachers;
- have 540 percent more police officers;
- have twice as many firefighters;
- produce 2.4 times more oil—as known reserves of oil grow;
- produce 2.67 times more cubic feet of lumber—as America’s supply of lumber stands grows;
- have conquered most of the infectious diseases that were major killers in the past.* 
The fact is that America today is much wealthier, healthier, spacious, and resource-rich than it was a century ago. And we owe many of these advances to the creativity and effort of immigrants. If open immigration worked until 1924 to enrich America, it can do so now with even greater certainty. Let’s welcome more immigrants so that they can help themselves, and us, build even better lives.
* My principal data sources for this article are Julian L. Simon, ed., The State of Humanity  (Blackwell, 1995), and Julian L. Simon, The Ultimate Resource 2  (Princeton University Press, 1996), as well as various U.S. Census Bureau reports.