America has gotten big dividends from its open-door immigration policy, you know

Much of the growth of the last two decades has stemmed from the vast capacity that was delivered by the Internet and the personal computer, each of which was accelerated by immigrant ingenuity. Silicon Valley, especially, was transformed. In a state where Asian immigrants had once faced great hardship, they helped to transform the global economy. The 2010 census stated that more than 50 percent of technical workers in Silicon Valley are Asian-American.

Google was co-founded by Sergey Brin, who emigrated from the Soviet Union with his parents at age 6. The new C.E.O. of United Airlines is Mexican-American. And an extraordinary number of Indian-Americans have risen to become chief executives of other major American corporations, including Adobe Systems, Pepsi, Motorola and Microsoft.

In countless other ways, as well, we might measure the improvements since 1965. A prominent AIDS researcher, David Ho, came to this country as a 12-year-old from Taiwan. Immigrants helped take the space program to new places, and sometimes gave their lives in that cause (an Indian-American astronaut, Kalpana Chawla, perished in the Columbia space shuttle disaster). Almost no one would argue for a return to pre-1965 American cuisine, which became incomparably more interesting as it grew more diverse. Baseball has become a more dynamic game as it, too, has looked south and west. The list goes on and on.