(Graphs from Alesina, Glaeser, and Sacerdote's "Why Doesn't the United States Have a European-Style Welfare State?")
Caplan thinks that the end of the journey is not only possible, but desirable. Key paragraphs :
"Diversity undermines solidarity. People don't mind paying high taxes to support people "like them." But free money for "the other" leads to resentment and political pushback.
That's exactly what we're seeing in the UK, and why Osborne and Shapps may get away politically with a real-terms benefits cut. They noted the outrage among working people in 2011 when benefits rose by 5% at a time of static wages.
If you're a social democrat, this implies a tragic trade-off between social justice for natives and social justice for potential immigrants. But if you're a libertarian, the opposite is true. The welfare state doesn't make open borders impossible. It's open borders that makes the eventual abolition of the welfare state imaginable."
Caveat - the first graph is based on 1990-1998 figures, the second on 1998 figures. Ireland and the UK, for example, are considerably more diverse than they were then. And the US is a lot more Hispanic than it was in 1998.
UPDATE - another academic blogger takes issue with Prof. Caplan - no comfort here, I fear:
" In particular, let me stress once again that even if open borders makes the majority population more anti-government, after a while their preferences will not matter, since they will inevitably become a minority of voters. "But at some stage the money runs out, no matter what the voters want.
Prof Caplan responds - no comfort again :
Can't say we've not been warned.
"The claim isn't that open borders will "destroy" solidarity or the welfare state, but merely that open borders will undermine both. And while free-marketers may well agree that some degree of solidarity is good, it's also hard for free-marketers to deny that current levels of solidarity are excessive. Solidarity stands in the way of free-market reforms in pensions, education, health care, taxation, agricultural policy, and much more."