Increased immigration would boost the U.S. economy. Immigrants are 30 percent more likely to start new businesses than native-born Americans, according to a research summary by Michael Greenstone and Adam Looney of The Hamilton Project. They are more likely to earn patents. A quarter of new high-tech companies with more than $1 million in sales were also founded by the foreign-born. A study by Madeline Zavodny, an economics professor at Agnes Scott College, found that every additional 100 foreign-born workers in science and technology fields is associated with 262 additional jobs for U.S. natives.
Immigration Is the Easy Problem, by David Brooks in an op-ed for the NYT, sheds light on immigration. This is probably true in European countries too.