Douthat on the real purpose of "immigration reform"

From the NYT:

When Assimilation Stalls 

By ROSS DOUTHAT 

THE immigration legislation percolating in the Senate ... real priority is to accelerate existing immigration trends. The enforcement mechanisms phase in gradually, with ambiguous prospects for success, while the legislation’s impact on migration would be immediate: more paths to residency for foreigners, instant legal status for the 11 million here illegally, and the implicit promise to future border-crossers that some kind of amnesty always comes to those who come and wait. 

Today, almost 25 percent of working-age Americans are first-generation immigrants or their children. That figure is up sharply since the 1960s, and it’s projected to climb to 37 percent by 2050. A vote for the Senate legislation would be a vote for that number to climb faster still. 

The bill has been written this way because America’s leadership class, Republicans as well as Democrats, assumes that continued mass immigration is exactly what our economy needs. As America struggles to adapt to an aging population, the bill’s supporters argue, immigrants offer youth, vitality and tax dollars. As we try to escape economic stagnation, mass immigration promises an extra shot of growth. 

Is there any reason to be skeptical of this optimistic consensus? Actually, there are two: the assimilation patterns for descendants of Hispanic (particularly Mexican) immigrants and the socioeconomic disarray among the native-born poor and working class. 

Conservatives have long worried that recent immigrants from Latin America would assimilate more slowly than previous new arrivals — because of their sheer numbers and shared language, and because the American economy has changed in ways that make it harder for less-educated workers to assimilate and rise. 

As my colleague David Leonhardt wrote recently, those fears seem unfounded if you look at second-generation Hispanics, who make clear progress — economic, educational and linguistic — relative to their immigrant parents.
But there’s a substantial body of literature showing that progress stalling out, especially for Mexican-Americans, between the second generation and the third. A 2002 study, for instance, reported that despite “improvements in human capital and earnings” for second-generation Mexican immigrants, the third generation still “trails the education and earnings of the average American,” and shows little sign of catching up. In their 2009 book “Generations of Exclusion,” the sociologists Edward Telles and Vilma Ortiz found similar stagnation and slippage for descendants of Mexican immigrants during the second half of the 20th century.