Letting in a low-skilled immigrant to mow my lawn will indeed lower average productivity in this country. But I will be better off.
Indeed, if we let in a single low-skilled immigrant just to do services for Arnold Kling, Arnold Kling will benefit, but only at the expense of other American taxpayers who have to pay his servant's carrying costs.
In a modern welfare state, letting in low skilled, low IQ, low wage immigrants, lowers the standard of living of non-immigrants because they have to pay for the immigrants’ carrying costs.
All levels of government in the United States spend approximately $16,800 per person per year ($5.1105 trillion of spending divided by 304.2 million people). A guy who mows lawns does not pay $16,800 of taxes, thus his labor is being heavily subsidized by the American taxpayer.
In fact, if the immigrant works 40 hours per week, he needs to earn more than $8.07/hour just to make as much money as the government is spending on his support. I don’t know how you can say that an immigrant is adding to the economy if the market value of his labor is less than what it costs the government to subsidize him. If a business owned a machine that produced $15,000 per year of output, but cost $16,8000 per year to maintain, the machine would be sold for scrap. Of course that assumes that the business is paying the machine’s costs. If the government were paying for the machine, then of course the business would keep it, because all businesses are glad to take corporate welfare from the government. Immigration is a form of corporate welfare.
We should also consider that immigrants become citizens and then vote in elections. If they are poor, they will vote for politicians who promise to increase government spending for poor people. It’s strange that a libertarian like Arnold Kling promotes a government immigration policy that’s guaranteed to result in a bigger welfare state.
How much money does an immigrant have to earn before the value that his labor adds to the economy plus the amount of taxes that he pays equals $16,800 per year? To be on the safe side, we should insist that an immigrant be able to earn at least twice that amount, $33,600 per year or $16.14 per hour, before he’s allowed to move here. The $33,600 per year worker still doesn't pay his share of taxes, but there's a chance that the value of his labor plus his taxes paid makes his presence worthwhile.
Hardly any illegal immigrants earn $33,600 per year, so all illegal immigrants should be deported.