Aren't more than a fifth of PhD holders in the U.S. foreign born? The story of immigrants returning home is a lot different from a story of native-born Americans abandoning their country.
The problem is that since WWII, the vast majority of these foreign born scientists in the US tended to stay and become naturalized U.S. citizens. It was uncommon, if not rare, for them to leave. In fact, there were waitlists for scientists trying to immigrate _into_ the U.S.
The reason for this was very much economic. The U.S., the leader in scientific spending over many decades after WWII, could pay scientists more than how much their home countries could pay. I should also note that in the past, the U.S. was also much more accomodating toward foreign born scientists in regard to naturalization, as well as popular attitude.
Now on every other bulletin board in my building, there're flyers in Chinese advertising very well-paid positions in China, and I get to read about the growing percentage of climate change deniers and creationists in the U.S almost every other week in the NY Times.
It is a very different situation, and the meaningfulness is likewise different. For a foreign-born PhD holder, they have family back there, they'll become bigger fish in a smaller pond, they already know the language, probably have citizenship, are acculturated, may not have kids and wives deeply embedded into American culture & communities, etc. For an American-born PhD holder, most of these will be false. The cost to an American of moving permanently overseas is, on average, going to be vastly higher to them.
When you hear of some foreign-born PhD holders on the margin deciding to return home, it's no big deal, and is adequately explained by very small shifts in the rewards of being in the US and the rewards of going home. (And a survey means even less.) People simply don't want to leave their home countries for very good reasons. Think of how few Jews left Nazi Germany before it was too late, even when the writing was literally on the wall (in the form of anti-semitic graffiti).
When you hear of a lot of American scientists leaving America permanently, then it's time to start panicking.
I got the hell out of the USA to go to grad school.
One thing that really helped is that when I visited one of my two grad-school options, the one inside the USA, the current grad-students told me there was no hope of ever getting a permanent research position, and that we could all expect to just drift from post-doc to post-doc before being discarded.
And this was a very good department for the field we were discussing. I adore these guys and their research.
At Technion, not only my advisor but other graduate students seem to feel they can safely assume they'll eventually find a well-paying industrial, academic, or governmental job with a Technion grad degree.
So, yeah, funny thing, making aliyah may well have been a good career move, which basically never happens. Oh, and speaking of antisemitic graffiti, once when I visited my cosmopolitan college town of Amherst, I found neo-Nazi graffiti about the Protocols of the Elders of Zion on an alley wall, and learned that UMass Amherst has a secret neo-Nazi club.
Be a little bit afraid.
Once I am done with graduate school I will be considering employment at a university oversees that appreciates it's scientists.
And it wouldn't be as difficult for many of these tenured professors to make the transition. They all collaborate with researchers oversees. They already have all the connections needed. Furthermore, the institutions over there would jump at opportunities to poach them.
Moving across the globe isn't nearly as difficult these days as it would have been in the 1930s.
And if moving across the globe would've fixed Americans' problems during the Great Depression I doubt they would've hesitated.
Folks, we are looking at the end of an empire.
[0] http://report.nih.gov/success_rates/ [1] http://report.nih.gov/DisplayRePORT.aspx?rid=601