Since North Korea is also competitive (12th this year, 5th in 2009) we should remark that it's South Korea that won this year (unexpectedly beating China, the usual winner - though it does always do well).
I was just reading a blog post from three years ago (yes, I have something I should be doing instead, why do you ask?) lamenting that in 2009 both Koreas beat the US, and blaming this on anti-mathematical culture in the US. I presume that the countries that do really well despite small populations do so by identifying likely competitors and getting them to focus on nothing else for a while (unlike most countries, where competitors fit in IMO training around their usual school and activities) but I don't actually know.
Actually Questions 1 and 2 are not too hard this year - for a mathematically trained adult who's not under pressure, that is! Have a go, you know you want to :-)
