Source: U.S. Department of Homeland Security
Source: U.S. Department of Homeland Security

For "a nation of immigrants," the U.S. is denying entry to a lot of foreigners who want to come here and would do a lot to grow our economy.

Just last month, Congress blocked a plan to offer more permanent-residency visas (green cards) to foreign doctorate and master's-degree students in science and technology fields. Republicans deliberately set up the bill to fail -- a bill which they ostensibly supported -- hoping to score political points and elicit campaign contributions from the technology industry, a Democratic-leaning constituency.

Republicans proposed to offer green cards to STEM (science, technology, engineering and mathematics) students who train at American universities and want to stay here and work, but they didn't want to increase the total number of immigration visas. So they made Democrats an offer they couldn't accept: They proposed to eliminate a visa program Democrats favor, a "diversity visa" which each year admits 55,000 people from countries that do not have large immigrant populations here.

With 60 percent of House members voting in favor, Republicans could still have easily passed the bill, H.R. 6249, through the House. But just to make sure it would be a political football instead of an actual law, they took it up "under suspension of the rules," a procedure that requires a two-thirds majority, and so it never got to the Senate. Keep in mind that this is the same House where Republicans have passed symbolic legislation to repeal the Affordable Care Act more than 30 times.

Given the tepid economic recovery, it’s sad that Congress cannot enact a pro-growth immigration policy. Giving citizenship or permanent residency to more high-skilled immigrants is perhaps the single-easiest way to grow the American economy. Science and technology companies face labor shortages in their industries, preventing expansion, and the students themselves want to stay here and make valuable contributions to research and business. All we have to do is let these people stay here and let American companies hire them.

The cost of failing to do so is large, as the American technology industry is deeply dependent on the talent of high-skilled immigrants. More than 20 percent of all Americans with degrees in science and engineering are foreign-born, meaning that immigrants are two-times overrepresented in these fields. It's even more concentrated in computer science and engineering: Immigrants make up almost a third of all degree holders in these sectors, both of which currently face severe shortages of talent.

The best economic research on high-skilled immigration, recently assembled here by the Kauffman Foundation, suggests extensive economic gains from growing America’s stock of human capital. For just one example, a disproportionate fraction of American startups and patents -- and that means jobs, too -- come from the entrepreneurship and ingenuity of our immigrants.

A new STEM visa program would be good, but it would be better to simply expand the number of green cards issued based on "employment-based preferences." These visas go to immigrants who come here to do work with outstanding qualifications in their fields. They are scientists of "sustained national or international acclaim and recognition." They are the world's best teachers and researchers, who want to work in our universities. They are holders of advanced degrees with five years or more of professional experience or have at least two years' worth of training in specialized fields.

And yet, we only admit about 140,000 of them a year. That's just 13 percent of the total number of permanent-residency visas granted in 2011. Why on Earth do we not want this talent? The world's brightest want to bring their human capital to the U.S., and we turn them away. All we have to do is open the door: These employment immigration visa programs are routinely oversubscribed, and the number of visas available has not grown in ten years, as shown by the accompanying graph.

Let's hope we don't realize the magnitude of our error only when we stop winning Nobel prizes in science, or when the next tech breakthrough comes from a graduate of an American university who we've forced to live and work abroad. If the U.S. wants to lead the world in research and innovation, we have to let the innovators come here and work.

(Evan Soltas is a contributor to the Ticker. Follow him on Twitter.)

Read more breaking commentary from Bloomberg View at the Ticker.