Two billion is a crazy population prediction even if open borders was enacted. Relative quality of life would decline very quickly with open borders, and the immigration level would slow down dramatically.

I also read some estimate that "only" 500 Million people world wide want to immigrate to the US. Overall I expect the quality-of-life gap between USA and the 3rd world to continue declining over the next couple decades.

I'll bet a thousand 2014 dollars at even odds that it's less than a quarter of that.

(Clarification: I'm talking about the population of the US, as per the PredictionBook entry, not of North America as per Moldbug's quote; the population of the latter is already over 500 million. Should probably stipulate present borders too, just in case. 2 billion isn't credible in any case, though.)

Yudkowsky's recent pwnedness

I'm not under the impression he was much less pwned in 2007. Are you thinking of something in particular?

As a counterpoint look at the rise of anti-immigration movements in Europe and e.g. the success of Marine Le Pen in France.

Is this post just an excuse for an NRxic quote? And what does the "Yudkowsky's recent pwnedness" swipe refer to?

I'm dubious about borders getting opened that soon, considering how long it's taking to make moderate moves towards drug legalization.

Curiously, the anti-immigration movement in the US would be very different than those in Western Europe, and, I would guess, significantly weaker. While economic arguments are somewhat similar in both countries (although e.g. studies differ whether (and what level of) immigration actually increases unemployment levels as in the short run immigrants seem to go to the countries where the unemployment is decreasing), in Western Europe immigrants are vastly overrepresented in crime statistics compared to local population, which is not the case in the US. Nor (it was my impression, I am not from the US) immigrants are often thought as a demographic group whose individuals are the most prone to commit crimes (it must be noted, however, that immigrants aren't a homogeneous group (both in Western Europe and the US) and their effect (and/or the perception thereof) on a country of destination might differ), and as they are not at the top of crime statistics, they are less likely to be a target of blame. Furthermore, it was my impression that due to the long history of immigration, the national identity of the US is not based on ethnicity, while in most European countries it definitely is. As you can see, it is not surprising that Americans are somewhat more likely than Europeans to think that immigration should be increased, and about two thirds of them think that on the whole immigration is a good thing, only in Sweden we find similar support for it.

Nevertheless, even given this unusually positive attitude towards immigration, I would guess that the US population reaching even 600 million (let alone 2 billion, which I believe must have been a hyperbole) by 2038 (U.S. Census Bureau projects approximately 400 millions) has a probability less than 1-2 percent. The reason is that while for a pundit it is often a good strategy to make bold claims about e.g. opening all borders, as it gains him attention (therefore I can believe that we will hear a lot of such claims from people who compete for attention) whether or not the claims about doubling World's GDP are correct (in the long run it may be correct, I do not know), it might not be such a good thing for a politician or a civil servant to do bold actions as it is a risk of losing control of the situation and/or getting fired, and, as a general rule, politicians and civil servants want neither of those, therefore , I would guess, they have to more cautious when they become actual decision makers. Therefore, even if one wants to promote the idea of open borders and free mobility, one could probably try to encourage more Schengen/EU style regional agreements and then gradually "merging" them with new bilateral agreements between those unions, as it seems less risky than simply welcoming all immigrants. And in the far future it may happen that large parts of the world is covered by a Schengen-like agreement making "nobody illegal" in a similar sense that it is relatively easy for a person from one EU country to work in another. But that would probably take much more than 25-30 years. However, I would guess that even then it seems highly unlikely that US population would exceed even 1 billion, let alone 2 billion, since as the economies of the developing countries improve, there will be less incentives for people to leave them for the US. One would expect a huge influx of immigrants only if US government loosens immigration restrictions "faster" than developing countries manage to improve.