Euro Nobels

This year Nobel prizes, to date, are a sweep for Europe.
Is this a trend, or a fluke?

Before world war 2, Europe dominated Nobel prize winnings, in the sciences and medicine, after the second world war, the US rapdily developed dominance, partly by virtue of having brought over a lot of the best European scientists - the US paid better, had more and more stable research funding, and had much better research facilities.
List of Nobel prize winners by nationality - note that a lot of the winners post-WWII lived in the US at the time they won the prize. eg in the 70s, 6 out of 20 US winners in the sciences were foreign, as were 13 out of 29 in the 80s (I counted foreign scientists but all Nobels - so the eco/peace/lit Nobels are in the total but the foreign recipients that were in the US at time of winning are not in the list of foreigners).
Things get complicated - eg Sydney Brenner is a South African, educated in the UK and had positions in the UK and US when he won the prize. You win a prize, everyone wants a piece of you. Interestingly, a quick scan suggests the UK, of all the other countries, is the only one with comparable fraction of foreign nationals winning for work done in the UK.

It took Europe 20-40 years to recover from the war, but starting in the 60s research was built back up to serious levels and is now, in my judgement, broadly on par with the US - in some areas Europe is ahead, in some areas the US is ahead.
This is partly seen in a reverse brain drain that I have argued is slowly developing.
That there was a brain drain from Europe to the US for decades in unarguable - I myself came to the US in part because conditions for research were better, there was simply more funding and more flexibility back when I were a lad.
I do not know that is the case any more.
The rest of the world is also catching up, and Asia will have a serious presence starting a few years ago.
We must remember that, contrary to Alfred's original intention, the prize is a lagging indicator, often the award lags the research by 20-40 years.

So, let's take a look at this year:
in Medicine we had two Brits and an Italian for stem cells - two of them are in the US, at Utah and UNC, one is at Cardiff.
Capecchi came to the US after the war as a child, and did all his work in the US; Smithies did his DPhil at Oxford post-war and then went to the US for a postdoc and stayed; Evans is the youngest, PhD from UCL in the 60s and he stayed in the UK.
Work was done in the 80s, when resources in the US were still clearly superior.

For physics, Fert and Grünberg are post-war students, PhD in the 60s, stayed in their home country, research done in the 80s.

In chemistry, Ertl has the same pattern. PhD in 60s, stayed at home for research.

It is too soon to call it a trend, the US will win plenty more Nobels, but it won't have the dominance it had in the 80s and 90s.
Interestingly, per capita the US doesn't look so hot. Even in the low decades, the UK and Netherlands have comparable per capita number of winners - overall in Europe the per capita win rate is lower, but post war that is driven by the big dip in per capita winners for Germany and France and Eastern Europe.
Scandinavia always had anomalously high per capita win rates, which may be a proximity effect, certainly it was in the early decades.

Interesting times.

PS: I should mention two other issues - large chunks of Europe were essentially out of the running for several decades, France and west Germany bounced back relatively quickly, but eastern Europe did not. Italy was also relatively unproductive, they lost a lot of their pre-war generation of scientists and post-war their science budget was poor and there were institutional problems - not enough openness and meritocracy within the universities and research institutions; Spain was worse, during Franco's era research suffered badly, and they are just now really recovering (but they really are, some excellent Spanish science being done now, with aggressive recruitment of Spanish expats).
Further, the EU has got into the fundamental research business in a serious way, and they provide better merit awards, more incentives for junior faculty, more mobility and more stable long term funding. It also makes it harder for US institutions to recruit future Nobel prize winners, which is a game they have played a lot, as noted in the comments.

All of this serves to make it likely that Europe will be, and remain, competitive on per capita or per economic size basis for research in the current era. The US is just now reacting to this, and both the US and Europe are starting to realise the East Asia is entering scientific research as a serious competitor.
All of this will reduce the US share of the Nobels compared to their peak, and I would not be surprised to see a clean sweep for Asia some year, maybe 20-30 years from now.