Comments
(My impression is German, especially in Switzerland, and following that Dutch, Norwegian and Swedish. It's interesting that north European and historically protestant countries are particularly strong; I believe these have especially strong ethoses of private charity, in particular the UK - think the Victorian culture of charity.)
These countries also have better education systems than the average European countries, see for instance here (I'm surprised Sweden is not in that global top20 but it's probably close). Edit: Norway is 21, Sweden 24. My guess is that this is more relevant. In fact, I'd be hesitant to even bet on a correlation between a country's tradition of charity and proneness to EA once you control for things like GDP. EAs tend to not be very influenced by tradition, plus quite a few EAs I know recount that they weren't involved in traditional do-good-activities at all before they encountered EA. Maybe things change once EA becomes more mainstream, but especially in the early phase where EA is something novel, I would not expect there to be much of a correlation.
According to World Giving Index (p. 11) the English-speaking countries have a much stronger tradition of private charity than Northern European countries such as Germany or the Scandinavian countries.
My guess is that in countries with a high tax ratio and a comprehensive welfare state, there is less private charity - partly because the citizens simply have less post-tax earnings, and partly because they think there is less need for it since their governments are better at solving social problems. For instance, Norway and Sweden give away a higher share of Gross National Income in development aid than any other country (more than 1 %).
At the same time, my own country, Sweden, is the most rationalist country in the world, according to World Values Survey. Also, Sweden has a very generous refugee politics and receives by far the most asylum seekers in the OECD, which indicates a high level of altruism. This means that Effective Altruism should have a huge potential in Sweden.
A hypothesis I have is that one reason why Effective Altruism hasn't taken off in Sweden (besides the fact that EA generally is strongest in the English-speaking world) is the said comparatively weak tradition of charitable giving in Sweden. Therefore, I think it might be wise to emphasize other aspects of the EA movement when trying to sell it in Sweden. The same goes for other similar countries.
I recently wrote an introduction to the EA movement in Swedish on my blog and hope to be able to publish on the same topic in mainstream newspapers later on.
My gut feeling is that a strong tradition (in Sweden, at least) of aversion to the methodological individualism at the core of the EA movement is a major factor behind this.
Methodological individualism is hard (if not outright impossible) to reconcile with the historical materialism that is Karl Marx's theory of history. The latter seems to be strongly held in many Scandinavian minds.
In short, I think many of the Swedes who care about alleviating poverty will think that the proper way to go about it is through changing the ownership of the means of production, not through increasing cost-effective philanthropy from the affluent.
Interesting stuff.
The UK gives an unusually high amount in government development aid too. And it does so quite effectively. It's almost enough to make me patriotic.
I'd encourage you to link your intro from the EA wiki.
I'm skeptical of this as an explanation, for basically two reasons:
I don't think this implication works either. Perhaps you could say admitting refugees is altruistic on a national scale, because the immigrants benefit but bring increased violent crime, especially rape, imposing a cost on the 'giver'. But what we're looking for is individual altruism, which we can't really infer from collective altruism: my self-interest is not the same as our collective self-interest, and there is little reason to think it is in my self-interest to vote for our collective self interest. Additionally, if you thought that immigration was a net good thing for the receiving country, accepting immigrants becomes self-interested rather than altruistic on a national level.