Malanga's piece doesn't really break new ground, but it's a worthwhile review of immigration's economic impacts on our economy. At one point he writes:
Estimates by pro-immigration forces that foreign workers contribute much more to the economy, boosting annual gross domestic product by hundreds of billions of dollars, generally just tally what immigrants earn here, while ignoring the offsetting effect they have on the wages of native-born workers.
Partway through that sentence, I thought Malanga was going to acquaint readers with an even more basic fact: Almost all of the economic output of immigrants goes to the immigrants themselves and thus benefits us about zilch. The $10-billion aggregate economic gain for the rest of us — in the context of a $12 trillion national economy — is, to use Peter Brimelow's word, nugatory. (Of course, this counts only crass economics. The mass-immigration-driven loss of comity across our society is a huge, non-quantified cost.)
Instead, Malanga went somewhere else with his thought. But it'll do for an apparent newcomer to the fray.
Coincidentally, the New York Times Magazine had a lengthy economics-of-immigration piece by Roger Lowenstein in its 7/9/06 issue. ("The Immigration Equation;" see Steve Sailer's detailed analysis here and five mostly-aware letters from NYT Magazine readers here [probably a time-limited link].)
Complementing the two points mentioned above, Lowenstein stumbled across a great central truth about immigration, but then he scampered away, unscathed by his encounter:
After all, 21 million immigrants, about 15 percent of the labor force, hold jobs in the U.S., but the country has nothing close to that many unemployed. (The actual number is only seven million.) So the majority of immigrants can't literally have "taken" jobs; they must be doing jobs that wouldn't have existed had the immigrants not been here.
In other words, if the immigrants weren't here, the jobs they're doing wouldn't be here, either, so we obviously wouldn't need the immigrants! QED.
New York-based writer Lawrence Auster made the same point memorably and in more detail in his 1997 booklet-length essay Huddled Cliches: Exposing the Fraudulent Arguments That Have Opened America's Borders to the World. Here's his ingenious thought experiment disproving the hackneyed assertion that "If we didn't have immigrants doing all kinds of jobs in America today, there would be nobody to do them.":
As Roy Beck demonstrated in his powerful account of American workers displaced by immigration, this widely believed idea is empirically false. It is also based on a false assumption. The assumption is that the American economy could only have developed in one way, with lots of immigrants coming here and taking lots of jobs. Therefore, the thinking goes, without the immigrants there would have been no one else to do those jobs and the economy would have been crippled.
In fact, most of those jobs only exist because of immigrants. We can illustrate this by means of a thought experiment. Imagine that back in the late nineteenth century there had been no Chinese Exclusion Act, and that large numbers of Chinese had continued to settle in California after 1882. Over the following decades, the Chinese would have filled all kinds of existing jobs in the California economy and would also have created new types of businesses and employment niches that hadn't existed before. Let us imagine further that in 1920 Californians began to call for immigration restrictions against the Chinese. The pro-immigration lobby in our fictional 1920 (using the same arguments that the pro-immigration lobby uses today) would have replied: "Without Chinese immigrants here, who would have done all these jobs?" The truth, of course, is that the Chinese in our imaginary 1920 are doing all those jobs only because they had come to America in the first place. Had there been no Chinese immigrants between 1882 and 1920, which was the actual case in the actual 1882-1920 period, California would have done just fine, as it in fact did.
From this we derive a maxim: Large-scale immigration creates the illusion of its own indispensability.
Huddled Cliches is available from the American Immigration Control Foundation. (Unfortunately, AICF has apparently run out of Auster's earlier, seminal work, The Path to National Suicide: An Essay on Immigration and Multiculturalism. But you can download a PDF version of it for free here.)