Immigration to the U.S. was open and free until 1914. Anyone who wanted to come just needed to get to Ellis Island and in they came, provided they brought no disease with them. But to survive here they had to work, so they did and the economy benefitted very nicely. More workers --> more goods and services --> more money --> more jobs --> more workers --. etc. A nice cycle. There was no real incentive to come to the U.S. unless you were willing to work or here was much better than home. Everybody benefitted by having the immigrants here.

In 1914 Congress restricted immigration because of war in the Naturalization Act.  That second condition, here is better than home, became a reality for a major part of the world population during World War I when huge numbers of displaced people came to Ellis Island, and borders were closed to preserve order.

The situation lightened some until the 1930's when the Democrats began establishing welfare programs. Welfare, when any citizen can demand money from the state and federal governments, adding a significant incentive to immigration. With this new influx, immigrants were now required to show they had a job here or that someone with a job would support them before they were admitted.

This requirement to keep immigrants off the welfare rolls had a big impact on the number of immigrants, and it was felt by the economy, especially in the 1960's.

So here is the problem: how to we get immigrants here who will work and not become a burden to the State? 

And there was one easy answer: illegal immigration. Illegal immigrants could never make welfare demands on the State so they were in the same situation as immigrants before 1914: come here, work to survive, and everyone benefits. This was especially good for the Boomers, the first generation to reestablish the caste system in middle-class America, where there were jobs too demeaning for them or their children. They needed somebody to do these jobs for them, like yardwork, cleaning, construction, etc., that they would never touch, having attended college.

Provided immigrants have no access to welfare, illegal immigration solved an important economic problem of closed borders in a welfare state.

Well, guess who messed-up this solution? The Democrats began, in the 1990's, passing more laws that allowed illegal immigrants to demand money from the State. Why did they do this? Because they cannot answer one question: at what point will we consider an illegal immigrant to have earned citizenship?

Until that question is answered, or until the middle- and upper-class consider yardwork and house-cleaning a good career, illegal immigration will remain a huge problem, economic and ethical.

But of course you can't deny welfare until there is a path to citizenship. This is a very important thing for the economy, and I wish they'd get on with answering that question. Five years of work to citizenship? Ten? Just make it some amount of work and I'm happy with it. But don't make it just being here feeding off Uncle Sam to earn citizenship. Make it something that demonstrates character.